change LoadEnvelope method

EnvelopeGenerator.Application/EnvelopeReceivers/Queries/ReadEnvelopeReceiverQuery.cs

@@ -1,6 +1,7 @@
 using EnvelopeGenerator.Application.Dto.EnvelopeReceiver;
 using EnvelopeGenerator.Application.Envelopes.Queries;
 using EnvelopeGenerator.Application.Exceptions;
+using EnvelopeGenerator.Application.Extensions;
 using EnvelopeGenerator.Application.Receivers.Queries;
 using EnvelopeGenerator.Extensions;
 using MediatR;
@@ -83,3 +84,12 @@ public record ReadEnvelopeReceiverQuery : IRequest<IEnumerable<EnvelopeReceiverD
     /// </summary>
     public ReadReceiverQuery? Receiver { get; set; }
 };
+
+public static class Extensions
+{
+    public static Task<EnvelopeReceiverDto?> ReadEnvelopeReceiverAsync(this IMediator mediator, string key)
+    {
+        var q = new ReadEnvelopeReceiverQuery() { Key = key };
+        return mediator.Send(q).Then(envRcvs => envRcvs.FirstOrDefault());
+    }
+}

EnvelopeGenerator.Application/Extensions/TaskExtensions.cs

@@ -36,4 +36,18 @@ public static class TaskExtensions
         var result = await task;
         return result?.Any() ?? false ? result : throw new NotFoundException(exceptionMessage);
     }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    /// <typeparam name="I"></typeparam>
+    /// <param name="task"></param>
+    /// <param name="act"></param>
+    /// <returns></returns>
+    public static async Task<I> Then<T, I>(this Task<T> task, Func<T, I> act)
+    {
+        var res = await task;
+        return act(res);
+    }
 }