Bug 45063 - Delegate System.Func<TestClass, TetsClassResult> does not take 2 arguments after recent Xamarin update
Summary: Delegate System.Func<TestClass, TetsClassResult> does not take 2 arguments af...
Alias: None
Product: Class Libraries
Classification: Mono
Component: General ()
Version: unspecified
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2016-10-05 14:37 UTC by Rob DeRosa
Modified: 2018-03-13 11:07 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Rob DeRosa 2016-10-05 14:37:04 UTC

After the recent Xamarin Studio (Mac OS) update I'm no longer able to build my PCL with Func<Arg1, TResult> class usage. For some reason it starts to complain that this func doesn't take two args:

Error CS1593: Delegate System.Func<TestClass, TetsClassResult> does not take 2arguments (CS1593) (MyPclLib)

If I create a new test project - it works fine with exactly the same code just with a simplified func method body:

public class MyClass
public MyClass ()
var array = new TestClass [] { new TestClass(), new TestClass() };
var any = array.Select<TestClass, TestClassResult> ((arg1, index) => {
return new TestClassResult (index);

public class TestClass

public class TestClassResult
public TestClassResult(int index)

Even if I simplify my original method it starts to work so I guess after the update Xamarin Studio fails to infer args usage and couldn't much the proper Func<> class, but I couldn't discover how to help it to find it.

Xamarin Studio information:

Xamarin Studio Enterprise
Version 6.1 (build 5441)
Installation UUID: e6dcef46-0a84-444e-bcfd-8be8b1a3b2b1
Mono 4.6.0 (mono-4.6.0-branch/746756c) (64-bit)
GTK+ 2.24.23 (Raleigh theme)

Package version: 406000245


Not Installed

Apple Developer Tools
Xcode 8.0 (11246)
Build 8A218a

Version: (Xamarin Enterprise)
Hash: 6c3fee4
Branch: xcode8
Build date: 2016-09-09 13:01:32-0400

Version: (Xamarin Enterprise)
Android SDK: /Users/username/Library/Developer/Xamarin/android-sdk-macosx
Supported Android versions:
4.0.3 (API level 15)
4.1 (API level 16)
4.2 (API level 17)
4.3 (API level 18)
4.4 (API level 19)
4.4.87 (API level 20)
5.0 (API level 21)
5.1 (API level 22)
6.0 (API level 23)
7.0 (API level 24)

SDK Tools Version: 25.2.2
SDK Platform Tools Version: 24.0.3
SDK Build Tools Version: 24.0.2

Java SDK: /usr
java version "1.8.0_101"
Java(TM) SE Runtime Environment (build 1.8.0_101-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)

Android Designer EPL code available here:

I have posted a question at SO:

Comment 1 Marek Safar 2016-10-05 16:02:55 UTC
Could you attach your project so we can reproduce it locally
Comment 2 Marek Safar 2018-03-13 11:07:08 UTC
We have not received the requested information. If you are still experiencing this issue please provide all the requested information and reopen the bug report.

Thank you!