Refactor and extend web API exception classes

- Replace AccessException with AccessDeniedException, supporting custom messages and generic type-based usage.
- Add generic versions for BadRequest, Duplicate, EntityNotFound, and Unauthorized exceptions.
- Allow custom error messages for all exception types.
- Improve XML documentation for clarity and consistency.
- Enhances flexibility and type safety for API error handling.

Author: Vadim Belov

Sources/EasyExtensions.AspNetCore/Exceptions/AccessDeniedException.cs

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2025–2026 Vadim Belov <https://belov.us>
+
+using System.Net;
+
+namespace EasyExtensions.AspNetCore.Exceptions
+{
+    /// <summary>
+    /// Represents an exception that is thrown when access to a specified object is denied due to insufficient
+    /// permissions.
+    /// </summary>
+    /// <param name="objectName">The name of the object for which access was denied. This value is used to identify the resource involved in the
+    /// access violation.</param>
+    /// <param name="message">The error message that explains the reason for the exception. If not specified, a default message of "Access
+    /// denied" is used.</param>
+    public class AccessDeniedException(string objectName, string message = "Access denied")
+        : WebApiException(HttpStatusCode.Forbidden, objectName, message) { }
+
+    /// <summary>
+    /// Represents an exception that is thrown when access to a resource of type T is denied, typically corresponding to
+    /// an HTTP 403 Forbidden response.
+    /// </summary>
+    /// <typeparam name="T">The type of the resource for which access was denied.</typeparam>
+    /// <param name="message">The error message that describes the reason for the access denial.</param>
+    public class AccessDeniedException<T>(string message = "Access denied")
+        : AccessDeniedException(typeof(T).Name, message) { }
+}

Sources/EasyExtensions.AspNetCore/Exceptions/AccessException.cs

@@ -6,10 +6,19 @@
 namespace EasyExtensions.AspNetCore.Exceptions
 {
     /// <summary>
-    /// Represents an exception that is thrown when a request is unauthorized or invalid for a specified object.
+    /// Represents an exception that is thrown to indicate a bad request (HTTP 400) in a web API operation.
     /// </summary>
-    /// <param name="objectName">The name of the object associated with the unauthorized or invalid request.</param>
-    public class BadRequestException(string objectName)
-        : WebApiException(HttpStatusCode.BadRequest, objectName, "Bad request")
-    { }
+    /// <param name="objectName">The name of the object or entity associated with the bad request. This value is used to provide context for the
+    /// error.</param>
+    /// <param name="message">The error message that describes the reason for the bad request. The default is "Bad request".</param>
+    public class BadRequestException(string objectName, string message = "Bad request")
+        : WebApiException(HttpStatusCode.BadRequest, objectName, message) { }
+
+    /// <summary>
+    /// Represents an exception that is thrown to indicate a bad request error associated with a specific resource type.
+    /// </summary>
+    /// <typeparam name="T">The type of the resource or entity related to the bad request.</typeparam>
+    /// <param name="message">The error message that describes the reason for the bad request. The default is "Bad request".</param>
+    public class BadRequestException<T>(string message = "Bad request")
+        : BadRequestException(typeof(T).Name, message) { }
 }

Sources/EasyExtensions.AspNetCore/Exceptions/BadRequestException.cs

@@ -12,7 +12,16 @@ namespace EasyExtensions.AspNetCore.Exceptions
     /// to indicate that a resource with the specified name already exists. Use this exception to signal duplicate
     /// creation attempts in resource management scenarios.</remarks>
     /// <param name="objectName">The name of the object that caused the conflict.</param>
-    public class DuplicateException(string objectName)
-        : WebApiException(HttpStatusCode.Conflict, objectName, "Object already exists")
-    { }
+    /// <param name="message">The error message that describes the reason for the conflict. The default is "Object already exists."</param>
+    public class DuplicateException(string objectName, string message = "Object already exists")
+        : WebApiException(HttpStatusCode.Conflict, objectName, message) { }
+
+    /// <summary>
+    /// Represents an exception that is thrown when an attempt is made to create or add a duplicate object of the
+    /// specified type.
+    /// </summary>
+    /// <typeparam name="T">The type of the object that caused the duplication error.</typeparam>
+    /// <param name="message">The error message that explains the reason for the exception. The default is "Object already exists."</param>
+    public class DuplicateException<T>(string message = "Object already exists")
+        : DuplicateException(typeof(T).Name, message) { }
 }

Sources/EasyExtensions.AspNetCore/Exceptions/DuplicateException.cs

@@ -10,7 +10,15 @@ namespace EasyExtensions.AspNetCore.Exceptions
     /// </summary>
     /// <param name="objectName">The name of the entity that was not found. This value is included in the exception details to identify the
     /// missing entity.</param>
-    public class EntityNotFoundException(string objectName)
-        : WebApiException(HttpStatusCode.NotFound, objectName, "Entity was not found")
-    { }
+    /// <param name="message">The error message that describes the reason for the exception. The default is "Entity was not found".</param>
+    public class EntityNotFoundException(string objectName, string message = "Entity was not found")
+        : WebApiException(HttpStatusCode.NotFound, objectName, message) { }
+
+    /// <summary>
+    /// Represents an exception that is thrown when an entity of the specified type cannot be found.
+    /// </summary>
+    /// <typeparam name="T">The type of the entity that was not found.</typeparam>
+    /// <param name="message">The error message that explains the reason for the exception. If not specified, a default message is used.</param>
+    public class EntityNotFoundException<T>(string message = "Entity was not found")
+        : EntityNotFoundException(typeof(T).Name, message) { }
 }

Sources/EasyExtensions.AspNetCore/Exceptions/EntityNotFoundException.cs

@@ -12,7 +12,16 @@ namespace EasyExtensions.AspNetCore.Exceptions
     /// API scenarios to indicate that the caller must authenticate or does not have permission to access the specified
     /// resource.</remarks>
     /// <param name="objectName">The name of the object or resource for which access was denied.</param>
-    public class UnauthorizedException(string objectName)
-        : WebApiException(HttpStatusCode.Unauthorized, objectName, "Unathorized")
-    { }
+    /// <param name="message">The error message that describes the reason for the unauthorized access. The default is "Unathorized".</param>
+    public class UnauthorizedException(string objectName, string message = "Unathorized")
+        : WebApiException(HttpStatusCode.Unauthorized, objectName, message) { }
+
+    /// <summary>
+    /// Represents an exception that is thrown when an operation is attempted without the required authorization for a
+    /// specific resource type.
+    /// </summary>
+    /// <typeparam name="T">The type of the resource or entity for which authorization failed.</typeparam>
+    /// <param name="message">The error message that explains the reason for the exception. The default is "Unathorized".</param>
+    public class UnauthorizedException<T>(string message = "Unathorized")
+        : UnauthorizedException(typeof(T).Name, message) { }
 }