Added a debug version of the Guard class so we get exceptions for debug asserts instead of a dialog.

src/ImageSharp/Common/Helpers/DebugGuard.cs

@@ -0,0 +1,33 @@
+// <copyright file="DebugGuard.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp
+{
+    using System;
+    using System.Diagnostics;
+
+    /// <summary>
+    /// Provides methods to protect against invalid parameters for a DEBUG build.
+    /// </summary>
+    [DebuggerStepThrough]
+    internal static class DebugGuard
+    {
+        /// <summary>
+        /// Verifies, that the method parameter with specified object value is not null
+        /// and throws an exception if it is found to be so.
+        /// </summary>
+        /// <param name="target">The target object, which cannot be null.</param>
+        /// <param name="parameterName">The name of the parameter that is to be checked.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="target"/> is null</exception>
+        [Conditional("DEBUG")]
+        public static void NotNull(object target, string parameterName)
+        {
+            if (target == null)
+            {
+                throw new ArgumentNullException(parameterName);
+            }
+        }
+    }
+}

src/ImageSharp/Common/Helpers/ThrowHelper.cs

@@ -1,26 +0,0 @@
-// <copyright file="ThrowHelper.cs" company="James Jackson-South">
-// Copyright (c) James Jackson-South and contributors.
-// Licensed under the Apache License, Version 2.0.
-// </copyright>
-
-namespace ImageSharp
-{
-    using System;
-    using System.Runtime.CompilerServices;
-
-    /// <summary>
-    /// Helps removing exception throwing code from hot path by providing non-inlined exception thrower methods.
-    /// </summary>
-    internal static class ThrowHelper
-    {
-        /// <summary>
-        /// Throws an <see cref="ArgumentNullException"/>
-        /// </summary>
-        /// <param name="paramName">The parameter name</param>
-        [MethodImpl(MethodImplOptions.NoInlining)]
-        public static void ThrowArgumentNullException(string paramName)
-        {
-            throw new ArgumentNullException(nameof(paramName));
-        }
-    }
-}

src/ImageSharp/Common/Memory/ArrayPointer{T}.cs

@@ -31,11 +31,7 @@ namespace ImageSharp
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public ArrayPointer(T[] array, void* pointerToArray, int offset)
         {
-            // TODO: Use Guard.NotNull() here after optimizing it by eliminating the default argument case and applying ThrowHelper!
-            if (array == null)
-            {
-                ThrowHelper.ThrowArgumentNullException(nameof(array));
-            }
+            DebugGuard.NotNull(array, nameof(array));
 
             this.Array = array;
             this.Offset = offset;
@@ -50,11 +46,7 @@ namespace ImageSharp
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public ArrayPointer(T[] array, void* pointerToArray)
         {
-            // TODO: Use Guard.NotNull() here after optimizing it by eliminating the default argument case and applying ThrowHelper!
-            if (array == null)
-            {
-                ThrowHelper.ThrowArgumentNullException(nameof(array));
-            }
+            DebugGuard.NotNull(array, nameof(array));
 
             this.Array = array;
             this.Offset = 0;

src/ImageSharp/Image/ImageBase{TColor}.cs

@@ -182,7 +182,7 @@ namespace ImageSharp
         /// </param>
         protected void CopyProperties(IImageBase other)
         {
-            Debug.Assert(other != null);
+            DebugGuard.NotNull(other, nameof(other));
 
             this.Configuration = other.Configuration;
         }

src/ImageSharp/MetaData/ImageFrameMetaData.cs

@@ -5,8 +5,6 @@
 
 namespace ImageSharp
 {
-    using System.Diagnostics;
-
     /// <summary>
     /// Encapsulates the metadata of an image frame.
     /// </summary>
@@ -28,7 +26,7 @@ namespace ImageSharp
         /// </param>
         internal ImageFrameMetaData(ImageFrameMetaData other)
         {
-            Debug.Assert(other != null);
+            DebugGuard.NotNull(other, nameof(other));
 
             this.FrameDelay = other.FrameDelay;
         }

src/ImageSharp/MetaData/ImageMetaData.cs

@@ -6,7 +6,6 @@
 namespace ImageSharp
 {
     using System.Collections.Generic;
-    using System.Diagnostics;
 
     /// <summary>
     /// Encapsulates the metadata of an image.
@@ -46,7 +45,7 @@ namespace ImageSharp
         /// </param>
         internal ImageMetaData(ImageMetaData other)
         {
-            Debug.Assert(other != null);
+            DebugGuard.NotNull(other, nameof(other));
 
             this.HorizontalResolution = other.HorizontalResolution;
             this.VerticalResolution = other.VerticalResolution;

src/ImageSharp/MetaData/ImageProperty.cs

@@ -6,7 +6,6 @@
 namespace ImageSharp
 {
     using System;
-    using System.Diagnostics;
 
     /// <summary>
     /// Stores meta information about a image, like the name of the author,
@@ -37,7 +36,7 @@ namespace ImageSharp
         /// </param>
         internal ImageProperty(ImageProperty other)
         {
-            Debug.Assert(other != null);
+            DebugGuard.NotNull(other, nameof(other));
 
             this.Name = other.Name;
             this.Value = other.Value;