Simplify Fluent theme registration in App.razor

Replaced custom Fluent theme registration (with ApplyToPageElements set to true) with the default Fluent theme registration, removing unnecessary property customization for a cleaner setup.

DbFirst.BlazorWebApp/Components/App.razor

@@ -5,10 +5,7 @@
     <meta charset="utf-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <base href="/" />
-    @DxResourceManager.RegisterTheme(Themes.Fluent.Clone(properties =>
-    {
-        properties.ApplyToPageElements = true;
-    }))
+    @DxResourceManager.RegisterTheme(Themes.Fluent)
     @DxResourceManager.RegisterScripts()
 
     <link href="_content/DevExpress.Blazor.Dashboard/ace.css" rel="stylesheet" />

DbFirst.BlazorWebApp/Components/BandEditor.razor

@@ -0,0 +1,55 @@
+<div class="band-editor">
+    <button class="band-editor-toggle" @onclick="() => IsExpanded = !IsExpanded">
+        <span class="band-editor-toggle-icon @(IsExpanded ? "expanded" : "")">&#9658;</span>
+        <span>Layout</span>
+    </button>
+    @if (IsExpanded)
+    {
+        <div class="band-editor-body">
+            <div class="band-controls">
+                <DxButton Text="Band hinzufügen" Click="OnAddBand" />
+                <DxButton Text="Layout speichern" Click="OnSaveLayout" Enabled="@CanSave" />
+                <DxButton Text="Layout zurücksetzen" Click="OnResetLayout" />
+            </div>
+            @foreach (var band in Bands)
+            {
+                <div class="band-row">
+                    <DxTextBox Text="@band.Caption" TextChanged="@(value => OnBandCaptionChanged.InvokeAsync((band, value)))" />
+                    <DxButton Text="Entfernen" Click="@(() => OnRemoveBand.InvokeAsync(band))" />
+                </div>
+            }
+            <DxFormLayout CssClass="band-columns" ColCount="2">
+                @foreach (var column in Columns)
+                {
+                    <DxFormLayoutItem Caption="@column.Caption">
+                        <DxComboBox Data="@BandOptions"
+                                    TData="BandOption"
+                                    TValue="string"
+                                    TextFieldName="Caption"
+                                    ValueFieldName="Id"
+                                    Value="@GetColumnBand(column.FieldName)"
+                                    ValueChanged="@(value => OnColumnBandChanged.InvokeAsync((column.FieldName, value)))"
+                                    Width="100%" />
+                    </DxFormLayoutItem>
+                }
+            </DxFormLayout>
+        </div>
+    }
+</div>
+
+@code {
+    private bool IsExpanded { get; set; }
+
+    [Parameter, EditorRequired] public List<BandDefinition> Bands { get; set; } = new();
+    [Parameter, EditorRequired] public List<BandOption> BandOptions { get; set; } = new();
+    [Parameter, EditorRequired] public List<ColumnDefinition> Columns { get; set; } = new();
+    [Parameter, EditorRequired] public Func<string, string> GetColumnBand { get; set; } = _ => string.Empty;
+    [Parameter, EditorRequired] public bool CanSave { get; set; }
+
+    [Parameter] public EventCallback OnAddBand { get; set; }
+    [Parameter] public EventCallback OnSaveLayout { get; set; }
+    [Parameter] public EventCallback OnResetLayout { get; set; }
+    [Parameter] public EventCallback<BandDefinition> OnRemoveBand { get; set; }
+    [Parameter] public EventCallback<(BandDefinition Band, string Value)> OnBandCaptionChanged { get; set; }
+    [Parameter] public EventCallback<(string FieldName, string? BandId)> OnColumnBandChanged { get; set; }
+}

DbFirst.BlazorWebApp/Components/BandGridBase.cs

@@ -0,0 +1,214 @@
+using DbFirst.BlazorWebApp.Models.Grid;
+using DbFirst.BlazorWebApp.Services;
+using DevExpress.Blazor;
+using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Components.Rendering;
+
+namespace DbFirst.BlazorWebApp.Components;
+
+public abstract class BandGridBase<TItem> : ComponentBase
+{
+    [Inject] protected BandLayoutService BandLayoutService { get; set; } = default!;
+
+    // --- Abstract: jedes Grid definiert diese selbst ---
+    protected abstract string LayoutKey { get; }
+    protected abstract List<ColumnDefinition> ColumnDefinitions { get; }
+
+    // --- Band-Layout Felder ---
+    protected BandLayout bandLayout = new();
+    protected Dictionary<string, string> columnBandAssignments = new();
+    protected List<BandOption> bandOptions = new();
+    protected Dictionary<string, ColumnDefinition> columnLookup = new();
+    protected string? layoutUser;
+    protected bool gridLayoutApplied;
+    protected IGrid? gridRef;
+
+    // --- SizeMode ---
+    protected SizeMode _sizeMode = SizeMode.Medium;
+    protected static readonly List<SizeMode> _sizeModes = Enum.GetValues<SizeMode>().ToList();
+
+    private const string LayoutType = "GRID_BANDS";
+
+    // --- Lifecycle ---
+    protected async Task InitializeBandLayoutAsync()
+    {
+        columnLookup = ColumnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
+        layoutUser = await BandLayoutService.EnsureLayoutUserAsync();
+        bandLayout = await BandLayoutService.LoadBandLayoutAsync(LayoutType, LayoutKey, layoutUser, columnLookup);
+        columnBandAssignments = BandLayoutService.BuildAssignmentsFromLayout(bandLayout);
+        ApplyColumnLayoutFromStorage();
+        _sizeMode = bandLayout.SizeMode;
+        UpdateBandOptions();
+    }
+
+    protected async Task ApplyGridLayoutAfterRenderAsync()
+    {
+        if (!gridLayoutApplied && gridRef != null && bandLayout.GridLayout != null)
+        {
+            gridRef.LoadLayout(bandLayout.GridLayout);
+            gridLayoutApplied = true;
+            await InvokeAsync(StateHasChanged);
+        }
+    }
+
+    // --- Layout speichern / zurücksetzen ---
+    protected async Task SaveLayoutAsync()
+    {
+        if (string.IsNullOrWhiteSpace(layoutUser)) return;
+        CaptureColumnLayoutFromGrid();
+        await BandLayoutService.SaveBandLayoutAsync(LayoutType, LayoutKey, layoutUser, bandLayout);
+    }
+
+    protected async Task ResetLayoutAsync()
+    {
+        if (string.IsNullOrWhiteSpace(layoutUser)) return;
+        await BandLayoutService.ResetBandLayoutAsync(LayoutType, LayoutKey, layoutUser);
+        bandLayout = new BandLayout();
+        columnBandAssignments.Clear();
+        UpdateBandOptions();
+        foreach (var column in ColumnDefinitions)
+            column.Width = null;
+        columnLookup = ColumnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
+        _sizeMode = SizeMode.Medium;
+        gridRef?.LoadLayout(new GridPersistentLayout());
+        gridLayoutApplied = false;
+    }
+
+    private void CaptureColumnLayoutFromGrid()
+    {
+        if (gridRef == null) return;
+        var layout = gridRef.SaveLayout();
+        bandLayout.GridLayout = layout;
+        bandLayout.SizeMode = _sizeMode;
+        var orderedColumns = layout.Columns
+            .Where(c => !string.IsNullOrWhiteSpace(c.FieldName))
+            .OrderBy(c => c.VisibleIndex)
+            .ToList();
+        bandLayout.ColumnOrder = orderedColumns.Select(c => c.FieldName).ToList();
+        bandLayout.ColumnWidths = orderedColumns
+            .Where(c => !string.IsNullOrWhiteSpace(c.Width))
+            .ToDictionary(c => c.FieldName, c => c.Width, StringComparer.OrdinalIgnoreCase);
+    }
+
+    private void ApplyColumnLayoutFromStorage()
+    {
+        foreach (var column in ColumnDefinitions)
+        {
+            if (bandLayout.ColumnWidths.TryGetValue(column.FieldName, out var width) && !string.IsNullOrWhiteSpace(width))
+                column.Width = width;
+        }
+        columnLookup = ColumnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
+    }
+
+    // --- Band-Methoden ---
+    protected bool CanSaveBandLayout => !string.IsNullOrWhiteSpace(layoutUser);
+
+    protected void AddBand()
+    {
+        bandLayout.Bands.Add(new BandDefinition { Id = Guid.NewGuid().ToString("N"), Caption = "Band" });
+        UpdateBandOptions();
+    }
+
+    protected void RemoveBand(BandDefinition band)
+    {
+        bandLayout.Bands.Remove(band);
+        foreach (var key in columnBandAssignments.Where(p => p.Value == band.Id).Select(p => p.Key).ToList())
+            columnBandAssignments.Remove(key);
+        UpdateBandOptions();
+        SyncBandsFromAssignments();
+    }
+
+    protected void UpdateBandCaption(BandDefinition band, string value)
+    {
+        band.Caption = value;
+        UpdateBandOptions();
+    }
+
+    protected void UpdateColumnBand(string fieldName, string? bandId)
+    {
+        if (string.IsNullOrWhiteSpace(bandId))
+            columnBandAssignments.Remove(fieldName);
+        else
+            columnBandAssignments[fieldName] = bandId;
+        SyncBandsFromAssignments();
+    }
+
+    protected string GetColumnBand(string fieldName)
+        => columnBandAssignments.TryGetValue(fieldName, out var bandId) ? bandId : string.Empty;
+
+    protected void SyncBandsFromAssignments()
+    {
+        foreach (var band in bandLayout.Bands)
+        {
+            band.Columns = ColumnDefinitions
+                .Where(c => columnBandAssignments.TryGetValue(c.FieldName, out var id) && id == band.Id)
+                .Select(c => c.FieldName)
+                .ToList();
+        }
+        StateHasChanged();
+    }
+
+    protected void UpdateBandOptions()
+    {
+        bandOptions = new List<BandOption> { new() { Id = string.Empty, Caption = "Ohne Band" } };
+        bandOptions.AddRange(bandLayout.Bands.Select(b => new BandOption { Id = b.Id, Caption = b.Caption }));
+    }
+
+    // --- SizeMode ---
+    protected string FormatSizeText(SizeMode size) => size switch
+    {
+        SizeMode.Small => "Klein",
+        SizeMode.Medium => "Mittel",
+        SizeMode.Large => "Groß",
+        _ => size.ToString()
+    };
+
+    protected void OnSizeChange(DropDownButtonItemClickEventArgs args)
+    {
+        _sizeMode = Enum.Parse<SizeMode>(args.ItemInfo.Id);
+    }
+
+    // --- RenderColumns / BuildDataColumn ---
+    protected RenderFragment RenderColumns() => builder =>
+    {
+        var seq = 0;
+        builder.OpenComponent<DxGridCommandColumn>(seq++);
+        builder.AddAttribute(seq++, "Width", "120px");
+        builder.CloseComponent();
+
+        var grouped = bandLayout.Bands.SelectMany(b => b.Columns).ToHashSet(StringComparer.OrdinalIgnoreCase);
+        foreach (var column in ColumnDefinitions.Where(c => !grouped.Contains(c.FieldName)))
+            BuildDataColumn(builder, ref seq, column);
+
+        foreach (var band in bandLayout.Bands)
+        {
+            if (band.Columns.Count == 0) continue;
+            builder.OpenComponent<DxGridBandColumn>(seq++);
+            builder.AddAttribute(seq++, "Caption", band.Caption);
+            builder.AddAttribute(seq++, "Columns", (RenderFragment)(bandBuilder =>
+            {
+                var bandSeq = 0;
+                foreach (var columnName in band.Columns)
+                {
+                    if (columnLookup.TryGetValue(columnName, out var column))
+                        BuildDataColumn(bandBuilder, ref bandSeq, column);
+                }
+            }));
+            builder.CloseComponent();
+        }
+    };
+
+    protected void BuildDataColumn(RenderTreeBuilder builder, ref int seq, ColumnDefinition column)
+    {
+        builder.OpenComponent<DxGridDataColumn>(seq++);
+        builder.AddAttribute(seq++, "FieldName", column.FieldName);
+        builder.AddAttribute(seq++, "Caption", column.Caption);
+        if (!string.IsNullOrWhiteSpace(column.Width))
+            builder.AddAttribute(seq++, "Width", column.Width);
+        if (!string.IsNullOrWhiteSpace(column.DisplayFormat))
+            builder.AddAttribute(seq++, "DisplayFormat", column.DisplayFormat);
+        if (column.ReadOnly)
+            builder.AddAttribute(seq++, "ReadOnly", true);
+        builder.CloseComponent();
+    }
+}

DbFirst.BlazorWebApp/Components/CatalogsGrid.razor

@@ -1,5 +1,5 @@
+@inherits BandGridBase<CatalogReadDto>
 @inject CatalogApiClient Api
-@inject BandLayoutService BandLayoutService
 
 @if (!string.IsNullOrWhiteSpace(errorMessage))
 {
@@ -24,44 +24,17 @@ else if (items.Count == 0)
 }
 else
 {
-    <div class="band-editor">
-        <button class="band-editor-toggle" @onclick="() => bandEditorExpanded = !bandEditorExpanded">
-            <span class="band-editor-toggle-icon @(bandEditorExpanded ? "expanded" : "")">&#9658;</span>
-            <span>Layout</span>
-        </button>
-        @if (bandEditorExpanded)
-        {
-            <div class="band-editor-body">
-                <div class="band-controls">
-                    <DxButton Text="Band hinzufügen" Click="AddBand" />
-                    <DxButton Text="Layout speichern" Click="SaveLayoutAsync" Enabled="@CanSaveBandLayout" />
-                    <DxButton Text="Layout zurücksetzen" Click="ResetLayoutAsync" />
-                </div>
-                @foreach (var band in bandLayout.Bands)
-                {
-                    <div class="band-row">
-                        <DxTextBox Text="@band.Caption" TextChanged="@(value => UpdateBandCaption(band, value))" />
-                        <DxButton Text="Entfernen" Click="@(() => RemoveBand(band))" />
-                    </div>
-                }
-                <DxFormLayout CssClass="band-columns" ColCount="2">
-                    @foreach (var column in columnDefinitions)
-                    {
-                        <DxFormLayoutItem Caption="@column.Caption">
-                            <DxComboBox Data="@bandOptions"
-                                        TData="BandOption"
-                                        TValue="string"
-                                        TextFieldName="Caption"
-                                        ValueFieldName="Id"
-                                        Value="@GetColumnBand(column.FieldName)"
-                                        ValueChanged="@(value => UpdateColumnBand(column.FieldName, value))"
-                                        Width="100%" />
-                        </DxFormLayoutItem>
-                    }
-                </DxFormLayout>
-            </div>
-        }
-    </div>
+    <BandEditor Bands="@bandLayout.Bands"
+                BandOptions="@bandOptions"
+                Columns="@ColumnDefinitions"
+                GetColumnBand="GetColumnBand"
+                CanSave="@CanSaveBandLayout"
+                OnAddBand="AddBand"
+                OnSaveLayout="SaveLayoutWithFeedbackAsync"
+                OnResetLayout="ResetLayoutWithFeedbackAsync"
+                OnRemoveBand="RemoveBand"
+                OnBandCaptionChanged="@(args => UpdateBandCaption(args.Band, args.Value))"
+                OnColumnBandChanged="@(args => UpdateColumnBand(args.FieldName, args.BandId))" />
 
     <div class="grid-section">
         <DxGrid Data="@items"
@@ -148,29 +121,21 @@ else
     private string? infoMessage;
     private EditContext? editContext;
     private ValidationMessageStore? validationMessageStore;
-    private IGrid? gridRef;
     private int? focusedRowKey;
     private string popupHeaderText = "Edit";
-    private const string LayoutType = "GRID_BANDS";
-    private const string LayoutKey = "CatalogsGrid";
-    private string? layoutUser;
-    private BandLayout bandLayout = new();
-    private Dictionary<string, string> columnBandAssignments = new();
-    private List<BandOption> bandOptions = new();
-    private Dictionary<string, ColumnDefinition> columnLookup = new();
-    private bool gridLayoutApplied;
-    private bool bandEditorExpanded;
 
-    private List<ColumnDefinition> columnDefinitions = new()
-    {
-        new() { FieldName = nameof(CatalogReadDto.Guid), Caption = "Id", Width = "140px", FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(CatalogReadDto.CatTitle), Caption = "Titel", FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(CatalogReadDto.CatString), Caption = "String", FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(CatalogReadDto.AddedWho), Caption = "Angelegt von", ReadOnly = true, FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(CatalogReadDto.AddedWhen), Caption = "Angelegt am", ReadOnly = true, FilterType = ColumnFilterType.Date },
-        new() { FieldName = nameof(CatalogReadDto.ChangedWho), Caption = "Geändert von", ReadOnly = true, FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(CatalogReadDto.ChangedWhen), Caption = "Geändert am", ReadOnly = true, FilterType = ColumnFilterType.Date }
-    };
+    protected override string LayoutKey => "CatalogsGrid";
+
+    protected override List<ColumnDefinition> ColumnDefinitions { get; } = new()
+{
+    new() { FieldName = nameof(CatalogReadDto.Guid),       Caption = "Id",          Width = "140px", FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(CatalogReadDto.CatTitle),   Caption = "Titel",                        FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(CatalogReadDto.CatString),  Caption = "String",                       FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(CatalogReadDto.AddedWho),   Caption = "Angelegt von", ReadOnly = true, FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(CatalogReadDto.AddedWhen),  Caption = "Angelegt am",  ReadOnly = true, FilterType = ColumnFilterType.Date },
+    new() { FieldName = nameof(CatalogReadDto.ChangedWho), Caption = "Geändert von", ReadOnly = true, FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(CatalogReadDto.ChangedWhen),Caption = "Geändert am",  ReadOnly = true, FilterType = ColumnFilterType.Date }
+};
 
     private readonly List<ProcedureOption> procedureOptions = new()
     {
@@ -178,44 +143,15 @@ else
         new() { Value = 1, Text = "PRTBMY_CATALOG_SAVE" }
     };
 
-    private bool CanSaveBandLayout => !string.IsNullOrWhiteSpace(layoutUser);
-
-    private SizeMode _sizeMode = SizeMode.Medium;
-    private static readonly List<SizeMode> _sizeModes = Enum.GetValues<SizeMode>().ToList();
-
-    private string FormatSizeText(SizeMode size) => size switch
-    {
-        SizeMode.Small => "Klein",
-        SizeMode.Medium => "Mittel",
-        SizeMode.Large => "Groß",
-        _ => size.ToString()
-    };
-
-    private void OnSizeChange(DropDownButtonItemClickEventArgs args)
-    {
-        _sizeMode = Enum.Parse<SizeMode>(args.ItemInfo.Id);
-    }
-
     protected override async Task OnInitializedAsync()
     {
-        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
-        layoutUser = await BandLayoutService.EnsureLayoutUserAsync();
-        bandLayout = await BandLayoutService.LoadBandLayoutAsync(LayoutType, LayoutKey, layoutUser, columnLookup);
-        columnBandAssignments = BandLayoutService.BuildAssignmentsFromLayout(bandLayout);
-        ApplyColumnLayoutFromStorage();
-        _sizeMode = bandLayout.SizeMode;
-        UpdateBandOptions();
+        await InitializeBandLayoutAsync();
         await LoadCatalogs();
     }
 
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {
-        if (!gridLayoutApplied && gridRef != null && bandLayout.GridLayout != null)
-        {
-            gridRef.LoadLayout(bandLayout.GridLayout);
-            gridLayoutApplied = true;
-            await InvokeAsync(StateHasChanged);
-        }
+        await ApplyGridLayoutAfterRenderAsync();
     }
 
     private async Task LoadCatalogs()
@@ -238,174 +174,6 @@ else
         }
     }
 
-    private async Task SaveLayoutAsync()
-    {
-        if (string.IsNullOrWhiteSpace(layoutUser))
-            return;
-
-        try
-        {
-            CaptureColumnLayoutFromGrid();
-            await BandLayoutService.SaveBandLayoutAsync(LayoutType, LayoutKey, layoutUser, bandLayout);
-            infoMessage = "Layout gespeichert.";
-            errorMessage = null;
-        }
-        catch (Exception ex)
-        {
-            errorMessage = $"Layout konnte nicht gespeichert werden: {ex.Message}";
-        }
-    }
-
-    private async Task ResetLayoutAsync()
-    {
-        if (string.IsNullOrWhiteSpace(layoutUser))
-            return;
-
-        await BandLayoutService.ResetBandLayoutAsync(LayoutType, LayoutKey, layoutUser);
-
-        bandLayout = new BandLayout();
-        columnBandAssignments.Clear();
-        UpdateBandOptions();
-
-        foreach (var column in columnDefinitions)
-            column.Width = null;
-        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
-
-        _sizeMode = SizeMode.Medium;
-
-        if (gridRef != null)
-            gridRef.LoadLayout(new GridPersistentLayout());
-        gridLayoutApplied = false;
-
-        infoMessage = "Layout zurückgesetzt.";
-        errorMessage = null;
-    }
-
-    private void CaptureColumnLayoutFromGrid()
-    {
-        if (gridRef == null)
-            return;
-
-        var layout = gridRef.SaveLayout();
-        bandLayout.GridLayout = layout;
-        bandLayout.SizeMode = _sizeMode;
-
-        var orderedColumns = layout.Columns
-            .Where(c => !string.IsNullOrWhiteSpace(c.FieldName))
-            .OrderBy(c => c.VisibleIndex)
-            .ToList();
-
-        bandLayout.ColumnOrder = orderedColumns.Select(c => c.FieldName).ToList();
-        bandLayout.ColumnWidths = orderedColumns
-            .Where(c => !string.IsNullOrWhiteSpace(c.Width))
-            .ToDictionary(c => c.FieldName, c => c.Width, StringComparer.OrdinalIgnoreCase);
-    }
-
-    private void ApplyColumnLayoutFromStorage()
-    {
-        foreach (var column in columnDefinitions)
-        {
-            if (bandLayout.ColumnWidths.TryGetValue(column.FieldName, out var width) && !string.IsNullOrWhiteSpace(width))
-                column.Width = width;
-        }
-        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
-    }
-
-    private void AddBand()
-    {
-        bandLayout.Bands.Add(new BandDefinition { Id = Guid.NewGuid().ToString("N"), Caption = "Band" });
-        UpdateBandOptions();
-    }
-
-    private void RemoveBand(BandDefinition band)
-    {
-        bandLayout.Bands.Remove(band);
-        foreach (var key in columnBandAssignments.Where(p => p.Value == band.Id).Select(p => p.Key).ToList())
-            columnBandAssignments.Remove(key);
-        UpdateBandOptions();
-        SyncBandsFromAssignments();
-    }
-
-    private void UpdateBandCaption(BandDefinition band, string value)
-    {
-        band.Caption = value;
-        UpdateBandOptions();
-    }
-
-    private void UpdateColumnBand(string fieldName, string? bandId)
-    {
-        if (string.IsNullOrWhiteSpace(bandId))
-            columnBandAssignments.Remove(fieldName);
-        else
-            columnBandAssignments[fieldName] = bandId;
-        SyncBandsFromAssignments();
-    }
-
-    private string GetColumnBand(string fieldName)
-        => columnBandAssignments.TryGetValue(fieldName, out var bandId) ? bandId : string.Empty;
-
-    private void SyncBandsFromAssignments()
-    {
-        foreach (var band in bandLayout.Bands)
-        {
-            band.Columns = columnDefinitions
-                .Where(c => columnBandAssignments.TryGetValue(c.FieldName, out var id) && id == band.Id)
-                .Select(c => c.FieldName)
-                .ToList();
-        }
-        StateHasChanged();
-    }
-
-    private void UpdateBandOptions()
-    {
-        bandOptions = new List<BandOption> { new() { Id = string.Empty, Caption = "Ohne Band" } };
-        bandOptions.AddRange(bandLayout.Bands.Select(b => new BandOption { Id = b.Id, Caption = b.Caption }));
-    }
-
-    private RenderFragment RenderColumns() => builder =>
-    {
-        var seq = 0;
-        builder.OpenComponent<DxGridCommandColumn>(seq++);
-        builder.AddAttribute(seq++, "Width", "120px");
-        builder.CloseComponent();
-
-        var grouped = bandLayout.Bands.SelectMany(b => b.Columns).ToHashSet(StringComparer.OrdinalIgnoreCase);
-        foreach (var column in columnDefinitions.Where(c => !grouped.Contains(c.FieldName)))
-            BuildDataColumn(builder, ref seq, column);
-
-        foreach (var band in bandLayout.Bands)
-        {
-            if (band.Columns.Count == 0) continue;
-
-            builder.OpenComponent<DxGridBandColumn>(seq++);
-            builder.AddAttribute(seq++, "Caption", band.Caption);
-            builder.AddAttribute(seq++, "Columns", (RenderFragment)(bandBuilder =>
-            {
-                var bandSeq = 0;
-                foreach (var columnName in band.Columns)
-                {
-                    if (columnLookup.TryGetValue(columnName, out var column))
-                        BuildDataColumn(bandBuilder, ref bandSeq, column);
-                }
-            }));
-            builder.CloseComponent();
-        }
-    };
-
-    private void BuildDataColumn(RenderTreeBuilder builder, ref int seq, ColumnDefinition column)
-    {
-        builder.OpenComponent<DxGridDataColumn>(seq++);
-        builder.AddAttribute(seq++, "FieldName", column.FieldName);
-        builder.AddAttribute(seq++, "Caption", column.Caption);
-        if (!string.IsNullOrWhiteSpace(column.Width))
-            builder.AddAttribute(seq++, "Width", column.Width);
-        if (!string.IsNullOrWhiteSpace(column.DisplayFormat))
-            builder.AddAttribute(seq++, "DisplayFormat", column.DisplayFormat);
-        if (column.ReadOnly)
-            builder.AddAttribute(seq++, "ReadOnly", true);
-        builder.CloseComponent();
-    }
-
     private void SetEditContext(EditContext context)
     {
         if (editContext == context) return;
@@ -575,4 +343,25 @@ else
         public int Value { get; set; }
         public string Text { get; set; } = string.Empty;
     }
+
+    private async Task SaveLayoutWithFeedbackAsync()
+    {
+        try
+        {
+            await SaveLayoutAsync();
+            infoMessage = "Layout gespeichert.";
+            errorMessage = null;
+        }
+        catch (Exception ex)
+        {
+            errorMessage = $"Layout konnte nicht gespeichert werden: {ex.Message}";
+        }
+    }
+
+    private async Task ResetLayoutWithFeedbackAsync()
+    {
+        await ResetLayoutAsync();
+        infoMessage = "Layout zurückgesetzt.";
+        errorMessage = null;
+    }
 }

DbFirst.BlazorWebApp/Components/MassDataGrid.razor

@@ -1,5 +1,5 @@
+@inherits BandGridBase<MassDataReadDto>
 @inject MassDataApiClient Api
-@inject BandLayoutService BandLayoutService
 
 @if (!string.IsNullOrWhiteSpace(errorMessage))
 {
@@ -25,44 +25,17 @@ else if (items.Count == 0)
 else
 {
     
-    <div class="band-editor">
-        <button class="band-editor-toggle" @onclick="() => bandEditorExpanded = !bandEditorExpanded">
-            <span class="band-editor-toggle-icon @(bandEditorExpanded ? "expanded" : "")">&#9658;</span>
-            <span>Layout</span>
-        </button>
-        @if (bandEditorExpanded)
-        {
-            <div class="band-editor-body">
-                <div class="band-controls">
-                    <DxButton Text="Band hinzufügen" Click="AddBand" />
-                    <DxButton Text="Layout speichern" Click="SaveLayoutAsync" Enabled="@CanSaveBandLayout" />
-                    <DxButton Text="Layout zurücksetzen" Click="ResetLayoutAsync" />
-                </div>
-                @foreach (var band in bandLayout.Bands)
-                {
-                    <div class="band-row">
-                        <DxTextBox Text="@band.Caption" TextChanged="@(value => UpdateBandCaption(band, value))" />
-                        <DxButton Text="Entfernen" Click="@(() => RemoveBand(band))" />
-                    </div>
-                }
-                <DxFormLayout CssClass="band-columns" ColCount="2">
-                    @foreach (var column in columnDefinitions)
-                    {
-                        <DxFormLayoutItem Caption="@column.Caption">
-                            <DxComboBox Data="@bandOptions"
-                                        TData="BandOption"
-                                        TValue="string"
-                                        TextFieldName="Caption"
-                                        ValueFieldName="Id"
-                                        Value="@GetColumnBand(column.FieldName)"
-                                        ValueChanged="@(value => UpdateColumnBand(column.FieldName, value))"
-                                        Width="100%" />
-                        </DxFormLayoutItem>
-                    }
-                </DxFormLayout>
-            </div>
-        }
-    </div>
+    <BandEditor Bands="@bandLayout.Bands"
+                BandOptions="@bandOptions"
+                Columns="@ColumnDefinitions"
+                GetColumnBand="GetColumnBand"
+                CanSave="@CanSaveBandLayout"
+                OnAddBand="AddBand"
+                OnSaveLayout="SaveLayoutWithFeedbackAsync"
+                OnResetLayout="ResetLayoutWithFeedbackAsync"
+                OnRemoveBand="RemoveBand"
+                OnBandCaptionChanged="@(args => UpdateBandCaption(args.Band, args.Value))"
+                OnColumnBandChanged="@(args => UpdateColumnBand(args.FieldName, args.BandId))" />
 
     <div class="mb-3 page-size-selector">
         <span class="page-size-label">Datensätze je Seite:</span>
@@ -178,28 +151,20 @@ else
     private string popupHeaderText = "Edit";
     private EditContext? editContext;
     private ValidationMessageStore? validationMessageStore;
-    private IGrid? gridRef;
     private int? focusedRowKey;
-    private const string LayoutType = "GRID_BANDS";
-    private const string LayoutKey = "MassDataGrid";
-    private string? layoutUser;
-    private BandLayout bandLayout = new();
-    private Dictionary<string, string> columnBandAssignments = new();
-    private List<BandOption> bandOptions = new();
-    private Dictionary<string, ColumnDefinition> columnLookup = new();
-    private bool gridLayoutApplied;
-    private bool bandEditorExpanded;
 
-    private List<ColumnDefinition> columnDefinitions = new()
-    {
-        new() { FieldName = nameof(MassDataReadDto.Id), Caption = "Id", Width = "90px", ReadOnly = true, FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(MassDataReadDto.CustomerName), Caption = "CustomerName", FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(MassDataReadDto.Amount), Caption = "Amount", DisplayFormat = "c2", FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(MassDataReadDto.Category), Caption = "Category", ReadOnly = true, FilterType = ColumnFilterType.Text },
-        new() { FieldName = nameof(MassDataReadDto.StatusFlag), Caption = "Status", ReadOnly = true, FilterType = ColumnFilterType.Bool },
-        new() { FieldName = nameof(MassDataReadDto.AddedWhen), Caption = "Added", ReadOnly = true, FilterType = ColumnFilterType.Date },
-        new() { FieldName = nameof(MassDataReadDto.ChangedWhen), Caption = "Changed", ReadOnly = true, FilterType = ColumnFilterType.Date }
-    };
+    protected override string LayoutKey => "MassDataGrid";
+
+    protected override List<ColumnDefinition> ColumnDefinitions { get; } = new()
+{
+    new() { FieldName = nameof(MassDataReadDto.Id),           Caption = "Id",           Width = "90px", ReadOnly = true, FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(MassDataReadDto.CustomerName), Caption = "CustomerName",                 FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(MassDataReadDto.Amount),       Caption = "Amount",       DisplayFormat = "c2", FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(MassDataReadDto.Category),     Caption = "Category",     ReadOnly = true, FilterType = ColumnFilterType.Text },
+    new() { FieldName = nameof(MassDataReadDto.StatusFlag),   Caption = "Status",       ReadOnly = true, FilterType = ColumnFilterType.Bool },
+    new() { FieldName = nameof(MassDataReadDto.AddedWhen),    Caption = "Added",        ReadOnly = true, FilterType = ColumnFilterType.Date },
+    new() { FieldName = nameof(MassDataReadDto.ChangedWhen),  Caption = "Changed",      ReadOnly = true, FilterType = ColumnFilterType.Date }
+};
 
     private readonly List<PageSizeOption> pageSizeOptions = new()
     {
@@ -215,44 +180,15 @@ else
         new() { Value = 0, Text = "PRMassdata_UpsertByCustomerName" }
     };
 
-    private bool CanSaveBandLayout => !string.IsNullOrWhiteSpace(layoutUser);
-
-    private SizeMode _sizeMode = SizeMode.Medium;
-    private static readonly List<SizeMode> _sizeModes = Enum.GetValues<SizeMode>().ToList();
-
-    private string FormatSizeText(SizeMode size) => size switch
-    {
-        SizeMode.Small => "Klein",
-        SizeMode.Medium => "Mittel",
-        SizeMode.Large => "Groß",
-        _ => size.ToString()
-    };
-
-    private void OnSizeChange(DropDownButtonItemClickEventArgs args)
-    {
-        _sizeMode = Enum.Parse<SizeMode>(args.ItemInfo.Id);
-    }
-
     protected override async Task OnInitializedAsync()
     {
-        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
-        layoutUser = await BandLayoutService.EnsureLayoutUserAsync();
-        bandLayout = await BandLayoutService.LoadBandLayoutAsync(LayoutType, LayoutKey, layoutUser, columnLookup);
-        columnBandAssignments = BandLayoutService.BuildAssignmentsFromLayout(bandLayout);
-        ApplyColumnLayoutFromStorage();
-        _sizeMode = bandLayout.SizeMode;
-        UpdateBandOptions();
+        await InitializeBandLayoutAsync();
         await LoadPage(0);
     }
 
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {
-        if (!gridLayoutApplied && gridRef != null && bandLayout.GridLayout != null)
-        {
-            gridRef.LoadLayout(bandLayout.GridLayout);
-            gridLayoutApplied = true;
-            await InvokeAsync(StateHasChanged);
-        }
+        await ApplyGridLayoutAfterRenderAsync();
     }
 
     private async Task LoadPage(int page)
@@ -288,160 +224,6 @@ else
         await LoadPage(0);
     }
 
-    private async Task SaveLayoutAsync()
-    {
-        if (string.IsNullOrWhiteSpace(layoutUser))
-            return;
-        try
-        {
-            CaptureColumnLayoutFromGrid();
-            await BandLayoutService.SaveBandLayoutAsync(LayoutType, LayoutKey, layoutUser, bandLayout);
-            infoMessage = "Layout gespeichert.";
-            errorMessage = null;
-        }
-        catch (Exception ex)
-        {
-            errorMessage = $"Layout konnte nicht gespeichert werden: {ex.Message}";
-        }
-    }
-
-    private async Task ResetLayoutAsync()
-    {
-        if (string.IsNullOrWhiteSpace(layoutUser))
-            return;
-        await BandLayoutService.ResetBandLayoutAsync(LayoutType, LayoutKey, layoutUser);
-        bandLayout = new BandLayout();
-        columnBandAssignments.Clear();
-        UpdateBandOptions();
-        foreach (var column in columnDefinitions)
-            column.Width = null;
-        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
-        _sizeMode = SizeMode.Medium;
-        if (gridRef != null)
-            gridRef.LoadLayout(new GridPersistentLayout());
-        gridLayoutApplied = false;
-        infoMessage = "Layout zurückgesetzt.";
-        errorMessage = null;
-    }
-
-    private void CaptureColumnLayoutFromGrid()
-    {
-        if (gridRef == null) return;
-        var layout = gridRef.SaveLayout();
-        bandLayout.GridLayout = layout;
-        bandLayout.SizeMode = _sizeMode;
-        var orderedColumns = layout.Columns
-            .Where(c => !string.IsNullOrWhiteSpace(c.FieldName))
-            .OrderBy(c => c.VisibleIndex)
-            .ToList();
-        bandLayout.ColumnOrder = orderedColumns.Select(c => c.FieldName).ToList();
-        bandLayout.ColumnWidths = orderedColumns
-            .Where(c => !string.IsNullOrWhiteSpace(c.Width))
-            .ToDictionary(c => c.FieldName, c => c.Width, StringComparer.OrdinalIgnoreCase);
-    }
-
-    private void ApplyColumnLayoutFromStorage()
-    {
-        foreach (var column in columnDefinitions)
-        {
-            if (bandLayout.ColumnWidths.TryGetValue(column.FieldName, out var width) && !string.IsNullOrWhiteSpace(width))
-                column.Width = width;
-        }
-        columnLookup = columnDefinitions.ToDictionary(c => c.FieldName, StringComparer.OrdinalIgnoreCase);
-    }
-
-    private void AddBand()
-    {
-        bandLayout.Bands.Add(new BandDefinition { Id = Guid.NewGuid().ToString("N"), Caption = "Band" });
-        UpdateBandOptions();
-    }
-
-    private void RemoveBand(BandDefinition band)
-    {
-        bandLayout.Bands.Remove(band);
-        foreach (var key in columnBandAssignments.Where(p => p.Value == band.Id).Select(p => p.Key).ToList())
-            columnBandAssignments.Remove(key);
-        UpdateBandOptions();
-        SyncBandsFromAssignments();
-    }
-
-    private void UpdateBandCaption(BandDefinition band, string value)
-    {
-        band.Caption = value;
-        UpdateBandOptions();
-    }
-
-    private void UpdateColumnBand(string fieldName, string? bandId)
-    {
-        if (string.IsNullOrWhiteSpace(bandId))
-            columnBandAssignments.Remove(fieldName);
-        else
-            columnBandAssignments[fieldName] = bandId;
-        SyncBandsFromAssignments();
-    }
-
-    private string GetColumnBand(string fieldName)
-        => columnBandAssignments.TryGetValue(fieldName, out var bandId) ? bandId : string.Empty;
-
-    private void SyncBandsFromAssignments()
-    {
-        foreach (var band in bandLayout.Bands)
-        {
-            band.Columns = columnDefinitions
-                .Where(c => columnBandAssignments.TryGetValue(c.FieldName, out var id) && id == band.Id)
-                .Select(c => c.FieldName)
-                .ToList();
-        }
-        StateHasChanged();
-    }
-
-    private void UpdateBandOptions()
-    {
-        bandOptions = new List<BandOption> { new() { Id = string.Empty, Caption = "Ohne Band" } };
-        bandOptions.AddRange(bandLayout.Bands.Select(b => new BandOption { Id = b.Id, Caption = b.Caption }));
-    }
-
-    private RenderFragment RenderColumns() => builder =>
-    {
-        var seq = 0;
-        builder.OpenComponent<DxGridCommandColumn>(seq++);
-        builder.AddAttribute(seq++, "Width", "120px");
-        builder.CloseComponent();
-        var grouped = bandLayout.Bands.SelectMany(b => b.Columns).ToHashSet(StringComparer.OrdinalIgnoreCase);
-        foreach (var column in columnDefinitions.Where(c => !grouped.Contains(c.FieldName)))
-            BuildDataColumn(builder, ref seq, column);
-        foreach (var band in bandLayout.Bands)
-        {
-            if (band.Columns.Count == 0) continue;
-            builder.OpenComponent<DxGridBandColumn>(seq++);
-            builder.AddAttribute(seq++, "Caption", band.Caption);
-            builder.AddAttribute(seq++, "Columns", (RenderFragment)(bandBuilder =>
-            {
-                var bandSeq = 0;
-                foreach (var columnName in band.Columns)
-                {
-                    if (columnLookup.TryGetValue(columnName, out var column))
-                        BuildDataColumn(bandBuilder, ref bandSeq, column);
-                }
-            }));
-            builder.CloseComponent();
-        }
-    };
-
-    private void BuildDataColumn(RenderTreeBuilder builder, ref int seq, ColumnDefinition column)
-    {
-        builder.OpenComponent<DxGridDataColumn>(seq++);
-        builder.AddAttribute(seq++, "FieldName", column.FieldName);
-        builder.AddAttribute(seq++, "Caption", column.Caption);
-        if (!string.IsNullOrWhiteSpace(column.Width))
-            builder.AddAttribute(seq++, "Width", column.Width);
-        if (!string.IsNullOrWhiteSpace(column.DisplayFormat))
-            builder.AddAttribute(seq++, "DisplayFormat", column.DisplayFormat);
-        if (column.ReadOnly)
-            builder.AddAttribute(seq++, "ReadOnly", true);
-        builder.CloseComponent();
-    }
-
     private void SetEditContext(EditContext context)
     {
         if (editContext == context) return;
@@ -523,18 +305,17 @@ else
             Category = editModel.Category,
             StatusFlag = editModel.StatusFlag
         };
-        try
+
+        var result = await Api.UpsertAsync(dto);
+        if (!result.Success)
         {
-            var saved = await Api.UpsertAsync(dto);
-            infoMessage = editModel.IsNew ? "MassData angelegt." : "MassData aktualisiert.";
-            focusedRowKey = saved.Id;
-            await LoadPage(pageIndex);
-        }
-        catch (Exception ex)
-        {
-            errorMessage = $"Fehler beim Speichern: {ex.Message}";
+            errorMessage = result.Error ?? "Speichern fehlgeschlagen.";
             e.Cancel = true;
+            return;
         }
+        infoMessage = editModel.IsNew ? "MassData angelegt." : "MassData aktualisiert.";
+        focusedRowKey = result.Value?.Id;
+        await LoadPage(pageIndex);
     }
 
     private void AddValidationError(MassDataEditModel editModel, string fieldName, string message)
@@ -575,4 +356,25 @@ else
         public int? Value { get; set; }
         public string Text { get; set; } = string.Empty;
     }
+
+    private async Task SaveLayoutWithFeedbackAsync()
+    {
+        try
+        {
+            await SaveLayoutAsync();
+            infoMessage = "Layout gespeichert.";
+            errorMessage = null;
+        }
+        catch (Exception ex)
+        {
+            errorMessage = $"Layout konnte nicht gespeichert werden: {ex.Message}";
+        }
+    }
+
+    private async Task ResetLayoutWithFeedbackAsync()
+    {
+        await ResetLayoutAsync();
+        infoMessage = "Layout zurückgesetzt.";
+        errorMessage = null;
+    }
 }

DbFirst.BlazorWebApp/Components/Pages/Dashboard.razor

@@ -67,11 +67,6 @@
 
     protected override async Task OnParametersSetAsync()
     {
-        if (dashboards.Count == 0)
-        {
-            await RefreshDashboards();
-        }
-
         var requestedId = string.IsNullOrWhiteSpace(DashboardId) || string.Equals(DashboardId, "default", StringComparison.OrdinalIgnoreCase)
             ? null
             : DashboardId;

DbFirst.BlazorWebApp/Components/Pages/Home.razor

@@ -31,8 +31,8 @@
 
     public class CarouselData
     {
-        public string Source { get; set; }
-        public string AlternateText { get; set; }
+        public string Source { get; set; } = string.Empty;
+        public string AlternateText { get; set; } = string.Empty;
 
         public CarouselData(string source, string alt)
         {

DbFirst.BlazorWebApp/Services/ApiClientHelper.cs

@@ -0,0 +1,60 @@
+using System.Net;
+using System.Net.Http.Json;
+
+namespace DbFirst.BlazorWebApp.Services;
+
+internal sealed class ProblemDetailsDto
+{
+    public string? Type { get; set; }
+    public string? Title { get; set; }
+    public string? Detail { get; set; }
+}
+
+internal static class ApiClientHelper
+{
+    public static async Task<string> ReadErrorAsync(HttpResponseMessage response)
+    {
+        string? problemTitle = null;
+        string? problemDetail = null;
+
+        try
+        {
+            var problem = await response.Content.ReadFromJsonAsync<ProblemDetailsDto>();
+            if (problem != null)
+            {
+                problemTitle = problem.Title;
+                problemDetail = problem.Detail ?? problem.Type;
+            }
+        }
+        catch { }
+
+        var status = response.StatusCode;
+        var reason = response.ReasonPhrase;
+        var body = await response.Content.ReadAsStringAsync();
+
+        string? detail = problemDetail;
+        if (string.IsNullOrWhiteSpace(detail) && !string.IsNullOrWhiteSpace(body))
+            detail = body;
+
+        return status switch
+        {
+            HttpStatusCode.BadRequest => $"Eingabe ungültig{FormatSuffix(problemTitle, detail, reason)}",
+            HttpStatusCode.NotFound => $"Nicht gefunden{FormatSuffix(problemTitle, detail, reason)}",
+            HttpStatusCode.Conflict => $"Konflikt{FormatSuffix(problemTitle, detail, reason)}",
+            HttpStatusCode.Unauthorized => $"Nicht autorisiert{FormatSuffix(problemTitle, detail, reason)}",
+            HttpStatusCode.Forbidden => $"Nicht erlaubt{FormatSuffix(problemTitle, detail, reason)}",
+            HttpStatusCode.InternalServerError => $"Serverfehler{FormatSuffix(problemTitle, detail, reason)}",
+            _ => $"Fehler {(int)status} {reason ?? string.Empty}{FormatSuffix(problemTitle, detail, reason)}"
+        };
+    }
+
+    private static string FormatSuffix(string? title, string? detail, string? reason)
+    {
+        var parts = new List<string>();
+        if (!string.IsNullOrWhiteSpace(title)) parts.Add(title);
+        if (!string.IsNullOrWhiteSpace(detail)) parts.Add(detail);
+        if (parts.Count == 0 && !string.IsNullOrWhiteSpace(reason)) parts.Add(reason);
+        if (parts.Count == 0) return string.Empty;
+        return ": " + string.Join(" | ", parts);
+    }
+}

DbFirst.BlazorWebApp/Services/CatalogApiClient.cs

@@ -34,7 +34,7 @@ public class CatalogApiClient
             return ApiResult<CatalogReadDto?>.Ok(payload);
         }
 
-        var error = await ReadErrorAsync(response);
+        var error = await ApiClientHelper.ReadErrorAsync(response);
         return ApiResult<CatalogReadDto?>.Fail(error);
     }
 
@@ -46,7 +46,7 @@ public class CatalogApiClient
             return ApiResult<bool>.Ok(true);
         }
 
-        var error = await ReadErrorAsync(response);
+        var error = await ApiClientHelper.ReadErrorAsync(response);
         return ApiResult<bool>.Fail(error);
     }
 
@@ -58,68 +58,9 @@ public class CatalogApiClient
             return ApiResult<bool>.Ok(true);
         }
 
-        var error = await ReadErrorAsync(response);
+        var error = await ApiClientHelper.ReadErrorAsync(response);
         return ApiResult<bool>.Fail(error);
     }
-
-    private static async Task<string> ReadErrorAsync(HttpResponseMessage response)
-    {
-        string? problemTitle = null;
-        string? problemDetail = null;
-
-        try
-        {
-            var problem = await response.Content.ReadFromJsonAsync<ProblemDetailsDto>();
-            if (problem != null)
-            {
-                problemTitle = problem.Title;
-                problemDetail = problem.Detail ?? problem.Type;
-            }
-        }
-        catch
-        {
-        }
-
-        var status = response.StatusCode;
-        var reason = response.ReasonPhrase;
-        var body = await response.Content.ReadAsStringAsync();
-
-        string? detail = problemDetail;
-        if (string.IsNullOrWhiteSpace(detail) && !string.IsNullOrWhiteSpace(body))
-        {
-            detail = body;
-        }
-
-        if (status == HttpStatusCode.Conflict)
-        {
-            return "Datensatz existiert bereits. Bitte wählen Sie einen anderen Titel.";
-        }
-        if (status == HttpStatusCode.BadRequest && (detail?.Contains("CatTitle cannot be changed", StringComparison.OrdinalIgnoreCase) ?? false))
-        {
-            return "Titel kann nicht geändert werden.";
-        }
-
-        return status switch
-        {
-            HttpStatusCode.BadRequest => $"Eingabe ungültig{FormatSuffix(problemTitle, detail, reason)}",
-            HttpStatusCode.NotFound => $"Nicht gefunden{FormatSuffix(problemTitle, detail, reason)}",
-            HttpStatusCode.Conflict => $"Konflikt{FormatSuffix(problemTitle, detail, reason)}",
-            HttpStatusCode.Unauthorized => $"Nicht autorisiert{FormatSuffix(problemTitle, detail, reason)}",
-            HttpStatusCode.Forbidden => $"Nicht erlaubt{FormatSuffix(problemTitle, detail, reason)}",
-            HttpStatusCode.InternalServerError => $"Serverfehler{FormatSuffix(problemTitle, detail, reason)}",
-            _ => $"Fehler {(int)status} {reason ?? string.Empty}{FormatSuffix(problemTitle, detail, reason)}"
-        };
-    }
-
-    private static string FormatSuffix(string? title, string? detail, string? reason)
-    {
-        var parts = new List<string>();
-        if (!string.IsNullOrWhiteSpace(title)) parts.Add(title);
-        if (!string.IsNullOrWhiteSpace(detail)) parts.Add(detail);
-        if (parts.Count == 0 && !string.IsNullOrWhiteSpace(reason)) parts.Add(reason);
-        if (parts.Count == 0) return string.Empty;
-        return ": " + string.Join(" | ", parts);
-    }
 }
 
 public record ApiResult<T>(bool Success, T? Value, string? Error)
@@ -128,9 +69,3 @@ public record ApiResult<T>(bool Success, T? Value, string? Error)
     public static ApiResult<T> Fail(string? error) => new(false, default, error);
 }
 
-internal sealed class ProblemDetailsDto
-{
-    public string? Type { get; set; }
-    public string? Title { get; set; }
-    public string? Detail { get; set; }
-}

DbFirst.BlazorWebApp/Services/MassDataApiClient.cs

@@ -36,12 +36,17 @@ public class MassDataApiClient
         return result ?? new List<MassDataReadDto>();
     }
 
-    public async Task<MassDataReadDto> UpsertAsync(MassDataWriteDto dto)
+    public async Task<ApiResult<MassDataReadDto?>> UpsertAsync(MassDataWriteDto dto)
     {
         var response = await _httpClient.PostAsJsonAsync($"{Endpoint}/upsert", dto);
-        response.EnsureSuccessStatusCode();
-        var payload = await response.Content.ReadFromJsonAsync<MassDataReadDto>();
-        return payload ?? new MassDataReadDto();
+        if (response.IsSuccessStatusCode)
+        {
+            var payload = await response.Content.ReadFromJsonAsync<MassDataReadDto>();
+            return ApiResult<MassDataReadDto?>.Ok(payload);
+        }
+
+        var error = await ApiClientHelper.ReadErrorAsync(response);
+        return ApiResult<MassDataReadDto?>.Fail(error);
     }
 
     public async Task<MassDataReadDto?> GetByCustomerNameAsync(string customerName)