Bug 9345 - async capturing of 'this' not working?
Summary: async capturing of 'this' not working?
Alias: None
Product: Xamarin Studio
Classification: Desktop
Component: Debugger ()
Version: unspecified
Hardware: PC Mac OS
: --- normal
Target Milestone: ---
Assignee: Jeffrey Stedfast
Depends on:
Reported: 2013-01-07 17:06 UTC by Jeffrey Stedfast
Modified: 2013-01-08 10:33 UTC (History)
2 users (show)

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

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Description Jeffrey Stedfast 2013-01-07 17:06:36 UTC
using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

namespace AsyncDebugging
	class MainClass
		int foo = 0;

		public async Task<int> HelloWorldAsync ()
			Stopwatch sw = Stopwatch.StartNew ();
			var task = Task<int>.Factory.StartNew (() => { Thread.Sleep (4 * 1000); return 10; });
			int result = await task;

			Console.WriteLine ("Hello, World! result = {0}; {1}ms", result, sw.ElapsedMilliseconds);
			return result + foo;

		public static void Main (string[] args)
			var app = new MainClass ();
			Task t = app.HelloWorldAsync ();
			t.Wait ();

			Console.WriteLine ("Done.");

If you set a breakpoint anywhere in HelloWorldAsync(), the variable 'this' does not seem to get captured (it doesn't appear in the "Locals" pad) when the breakpoint is hit.
Comment 1 Marek Safar 2013-01-08 04:51:44 UTC
It's captures otherwise the could would fail to run.

Looking at the generated code you can see

  .class nested private auto ansi sealed beforefieldinit '<HelloWorldAsync>c__async0'
  	extends [mscorlib]System.ValueType
  	implements [mscorlib]System.Runtime.CompilerServices.IAsyncStateMachine  {

    .field  assembly  class AsyncDebugging.MainClass $this
Comment 2 Jeffrey Stedfast 2013-01-08 10:33:40 UTC
fixed in git master, 3.1.x, and ui-refresh