ArgumentException : Cannot bind to the target method because its signature is not compatible with that of the delegate type.

[malibay81]

Dear Support,

following exception occurs when auto mapping a model with viewmodel with same methods but different parameters !

System.ArgumentException
  HResult=0x80070057
  Message=Cannot bind to the target method because its signature is not compatible with that of the delegate type.
  Source=System.Private.CoreLib
  StackTrace:
   at System.Reflection.RuntimeMethodInfo.CreateDelegateInternal(Type delegateType, Object firstArgument, DelegateBindingFlags bindingFlags)
   at System.Reflection.RuntimeMethodInfo.CreateDelegate(Type delegateType)
   at ServiceStack.AssignmentMember.CreateGetter() in C:\BuildAgent\work\912418dcce86a188\src\ServiceStack.Text\AutoMappingUtils.cs:line 1085
   at ServiceStack.AssignmentEntry..ctor(String name, AssignmentMember from, AssignmentMember to) in C:\BuildAgent\work\912418dcce86a188\src\ServiceStack.Text\AutoMappingUtils.cs:line 1048
   at ServiceStack.AssignmentDefinition.AddMatch(String name, AssignmentMember readMember, AssignmentMember writeMember) in C:\BuildAgent\work\912418dcce86a188\src\ServiceStack.Text\AutoMappingUtils.cs:line 1140
   at ServiceStack.AutoMappingUtils.<>c__DisplayClass27_0.<GetAssignmentDefinition>b__0(String <p0>) in C:\BuildAgent\work\912418dcce86a188\src\ServiceStack.Text\AutoMappingUtils.cs:line 457
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at ServiceStack.AutoMappingUtils.GetAssignmentDefinition(Type toType, Type fromType) in C:\BuildAgent\work\912418dcce86a188\src\ServiceStack.Text\AutoMappingUtils.cs:line 445
   at ServiceStack.AutoMappingUtils.PopulateFromPropertiesWithoutAttribute[To,From](To to, From from, Type attributeType) in C:\BuildAgent\work\912418dcce86a188\src\ServiceStack.Text\AutoMappingUtils.cs:line 598
   at UnitTests.AutoMapperTest.Test_PopulateFromPropertiesWithoutAttribute() in K:\Library II\4. VB\09 Tests\UnitTests\AutoMapperTest.cs:line 37

This is the test code I have created:

   [TestClass]
   public class AutoMapperTest
   {
      [TestMethod]
      public void Test_PopulateFromPropertiesWithoutAttribute  ()
      {
         MyModel     myModel     = new MyModel ();
         MyViewModel myViewModel = new MyViewModel ();
         myViewModel.MyProp = "Test";
         myModel.PopulateFromPropertiesWithoutAttribute (myViewModel, typeof(IgnoreOnPopulateAttribute));
         Assert.AreEqual (myModel.MyProp, myViewModel.MyProp);
      }

      class MyModel
      {
         public void MyMethode (string myProp)
         {
            MyProp = myProp;
         }

         public string MyProp { get; set; }
      }

      class MyViewModel
      {
         public void MyMethode ()
         {
            MyProp = "MyMethode";
         }

         public string MyProp { get; set; }
      }
   }

Please see also the attached gif for more information.

Could you verify and fix it please.

[mythz]

Are you using the latest ServiceStack v5.8? As I'm not able to repro this, I've added a test for this in this commit but it passes without Exception.

[malibay81]

Yes, I'm using the latest version of ServiceStack v5.8.
Updated today.

I verfied your example !

in your code the method "MyMethod" of the class "TestMethode2" must have the parameter !

      public class TestMethod2
      {
         public void MyMethod(string myProp)
         {
            MyProp = nameof(MyMethod);
         }
         public string MyProp { get; set; }
      }

Then you get also the exception.

Thanx for your reply

[mythz]

I don't understand, your TestMethod2 is exactly the same as mine, one has a parameter the other doesn't, I've even tried swapping it so TestMethod has the parameter, the test still passes.

Can you rewrite this test so it repros the issue:

public class TestMethod
{
    public void MyMethod(string myProp)
    {
        MyProp = myProp;
    }
    public string MyProp { get; set; }
}

public class TestMethod2
{
    public void MyMethod()
    {
        MyProp = nameof(MyMethod);
    }
    public string MyProp { get; set; }
}

[Test]
public void Does_not_try_to_map_methods()
{
    var from = new TestMethod();
    var to = new TestMethod2();
    from.MyProp = "Test";
    to.PopulateFromPropertiesWithoutAttribute(from, typeof(IgnoreDataMemberAttribute));
    Assert.That(from.MyProp, Is.EqualTo(to.MyProp));
}

[malibay81]

No, the code is not the same.

Change/swap the methods of the classes TestMethod and TestMethod2.

See commented code below.

public class TestMethod
{
    // Change this
    // public void MyMethod(string myProp)
    public void MyMethod()
    {
        MyProp = myProp;
    }
    public string MyProp { get; set; }
}

public class TestMethod2
{
    // Change this
    // public void MyMethod()
    public void MyMethod(string myProp)
    {
        MyProp = nameof(MyMethod);
    }
    public string MyProp { get; set; }
}

[Test]
public void Does_not_try_to_map_methods()
{
    var from = new TestMethod();
    var to = new TestMethod2();
    from.MyProp = "Test";
    to.PopulateFromPropertiesWithoutAttribute(from, typeof(IgnoreDataMemberAttribute));
    Assert.That(from.MyProp, Is.EqualTo(to.MyProp));
}

Why does the auto mapper try to map methods ?
It doesn't make sense to me.

[mythz]

AutoMapping is able to map calculated methods that matches the shape of object getter/setter delegates. I just needed a repro to identify the issue, which should now be resolved from this commit.

This change is available from v5.8.1 that's now available on MyGet.

[malibay81]

OK, it's working, thank you for the quick bugfix !

But I don't understand why the mapper try's to map methods !
Could you provide me an example implementation for that purpose ?

[mythz]

IIRC it was the original implementation for implementing getters/setters, but just tested that it's needed anymore so I've just removed it.