initial commit

DigitalData.Core.Exceptions/MappingResultNullException.cs

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+using AutoMapper;
+using AutoMapper.Internal;
+
+namespace DigitalData.Core.Exceptions
+{
+    /// <summary>
+    /// Represents errors that occur during mapping when the result is unexpectedly null.
+    /// This exception is specifically used to indicate that an AutoMapper mapping operation
+    /// resulted in a null object, which may suggest a misconfiguration or an issue with the source data.
+    /// </summary>
+    public class MappingResultNullException : AutoMapperMappingException
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MappingResultNullException"/> class with the source and destination types causing the error.
+        /// </summary>
+        /// <param name="sourceType">The source type of the mapping operation.</param>
+        /// <param name="destinationType">The destination type of the mapping operation.</param>
+        /// <param name="innerException">The exception that is the cause of the current exception, or a null reference if no inner exception is specified.</param>
+        public MappingResultNullException(Type sourceType, Type destinationType, Exception? innerException = null)
+            : base(FormatMessage(sourceType, destinationType), innerException, new TypePair(sourceType, destinationType))
+        {
+        }
+
+        /// <summary>
+        /// Formats the exception message to include detailed information about the mapping operation that failed.
+        /// </summary>
+        /// <param name="sourceType">The source type involved in the mapping operation.</param>
+        /// <param name="destinationType">The destination type involved in the mapping operation.</param>
+        /// <returns>A formatted string containing the error message.</returns>
+        private static string FormatMessage(Type sourceType, Type destinationType)
+        {
+            return $"Mapping from {sourceType.FullName} to {destinationType.FullName} resulted in a null object. " +
+                   "Hint: Ensure that the AutoMapper profile configuration for this mapping is correct.";
+        }
+    }
+}