Fix mapping to Nullable<Guid>

Author: Roman Rusov

.gitignore

@@ -8,6 +8,9 @@ TestResults
 ## Ignore Visual Studio temporary files, build results, and
 ## files generated by popular Visual Studio add-ons.
 
+# Visual Studio cache/options directory
+.vs/
+
 # User-specific files
 *.suo
 *.user

Slapper.AutoMapper.Tests/ConvertersTests/GuidConverterTests.cs

@@ -0,0 +1,20 @@
+using System;
+using NUnit.Framework;
+using static Slapper.AutoMapper.Configuration;
+
+namespace Slapper.Tests.ConvertersTests
+{
+    [TestFixture]
+    public class GuidConverterTests
+    {
+        private readonly GuidConverter converter = new GuidConverter();
+
+        [TestCase(typeof(Guid))]
+        [TestCase(typeof(Guid?))]
+        public void Can_Convert_To_Type(Type targetType)
+        {
+            // Act + Assert
+            Assert.True(this.converter.CanConvert(null, targetType)); // Input value does not matter, null is enough for the test.
+        }
+    }
+}

Slapper.AutoMapper.Tests/Slapper.Tests.csproj

@@ -45,6 +45,7 @@
   <ItemGroup>
     <Compile Include="ArrayTests.cs" />
     <Compile Include="ComplexMapsParentsAndChlidTest.cs" />
+    <Compile Include="ConvertersTests\GuidConverterTests.cs" />
     <Compile Include="EmptyList.cs" />
     <Compile Include="HashCollisionTests.cs" />
     <Compile Include="MapCollectionsTypedTest.cs" />

Slapper.AutoMapper/Slapper.AutoMapper.Configuration.cs

@@ -192,7 +192,8 @@ public object Convert(object value, Type type)
                 /// <returns>Boolean response.</returns>
                 public bool CanConvert(object value, Type type)
                 {
-                    return type == typeof(Guid);
+                    var conversionType = Nullable.GetUnderlyingType(type) ?? type;
+                    return conversionType == typeof(Guid);
                 }
 
                 /// <summary>