The Visual Studio .NET or Visual Studio 2005 debugger stops responding when it calls an XML Web Service in asynchronous mode (315624)

RESOLUTION

A console application that blocks the primary thread can receive the asynchronous response from the Web service during a debugging session. However, in this case, the application was launched in a single-threaded apartment.

Resolution 1

By default, .NET-connected console applications run in a multithreaded apartment (MTA). Therefore, you can resolve this problem by removing the STAThread attribute that appears before the Main function (see the sample code in step 10 of the "Steps to Reproduce the Behavior" section). This permits the application to retrieve the result from another thread in the MTA while the debugger is executing.

Resolution 2

A Microsoft Windows-based application should run its primary thread in a single-threaded apartment (the STAThread attribute). However, because a Windows application is event-driven, the blocking loop does not have to prevent shutdown. Therefore, you can also use an event-driven Windows client application to resolve this problem.

MORE INFORMATION

Steps to reproduce the behavior

To reproduce the behavior, follow these steps:

In Visual Studio .NET or in Visual Studio 2005, create a new Visual C# ASP.NET Web service project named MyWebService1.
In Solution Explorer, right-click Service1.asmx, and then click View Code to edit the code.
Remove the comments to turn on the HelloWorld sample method.
Save and then build the project.
Add a new Visual C# console application named MyClient to the solution that you created in step 1.
In Solution Explorer, right-click MyClient, and then click Add Web Reference.
Type the URL for the .asmx file of the MyWebService1 project that you created in step 1 (for example, http://localhost/MyWebService1/Service1.asmx), and then click Add Reference.
In Solution Explorer, right-click MyClient, and then click Add Reference.
In the Add Reference dialog box, click the .NET tab, and then click System.Windows.Forms.dll in the list. This reference permits the console application to display a message box. Click Select, and then click OK.

Note In Visual Studio 2005, you do not have to click Select.

Open Class1.cs in Visual Studio .NET or Program.cs in Visual Studio 2005, and then replace all of the code with the following sample code:

using System;
using System.Windows.Forms;
using System.Threading;

namespace myconsoleapp
{
	// Summary description for Class1.
	class Class1
	{
		// The main entry point for the application.
		// public static void Handler(IAsyncResult ar)
		public static void Handler(IAsyncResult ar)
		{
		// Retrieve the proxy object reference that is passed
		// to BeginSubmit().
		localhost.Service1 proxy = (localhost.Service1)ar.AsyncState; 
			
		// Use the proxy to retrieve the result that is returned
		// from the call. Pass in 'ar' so that the specific 
		// call can be identified.
		string ret = proxy.EndHelloWorld(ar);

		// Show the XML receipt to the user.
		MessageBox.Show(ret);
		}

		[STAThread]
		static void Main(string[] args)
		{
			localhost.Service1 obj = new localhost.Service1();
			obj.HelloWorld();
			System.IAsyncResult ar;
			ar = obj.BeginHelloWorld(new AsyncCallback(Handler),obj);
			while(ar.IsCompleted != true)
			{
				System.Threading.Thread.Sleep(1000);
			} 
		}
	}
}

In Solution Explorer, right-click MyClient, and then click Set As Startup Project. Build the project in release mode, and then press CTRL+F5 to run the project. A command window appears, and then a message box appears that contains the following message: Hello World
Build the project in debug mode, and then run the project.
The application stops responding.