I have this simple async call I am making. I want to follow the call to the DownloadDataTaskAsync method and step through into the Microsoft .NET framework source code.
using System;
using System.Net;
using System.Text;
using System.Threading.Tasks;
namespace WhereIsTheTaskSchedulerHere
{
class Program
{
static void Main(string[] args)
{
var task = GetData("http://sathyaish.net");
var buffer = task.Result;
var data = Encoding.ASCII.GetString(buffer);
Console.WriteLine(data);
Console.WriteLine("\nPress any key to continue...");
Console.ReadKey();
}
async static Task<byte[]> GetData(string url)
{
var client = new WebClient();
var data = await client.DownloadDataTaskAsync(url);
return data;
}
}
}
I followed the call in Reflector until the point that the code calls System.Net.WebClient.DownloadBits method. If the call was meant to be executed asynchronously, this method further schedules the work on a threadpool thread by calling the Asynchronous Programming Model (APM) method BeginGetResponse on the System.Net.WebRequest class.
Here is the code of the DownloadBits method from Reflector.
private byte[] DownloadBits(WebRequest request, Stream writeStream, CompletionDelegate completionDelegate, AsyncOperation asyncOp)
{
WebResponse response = null;
DownloadBitsState state = new DownloadBitsState(request, writeStream, completionDelegate, asyncOp, this.m_Progress, this);
if (state.Async)
{
request.BeginGetResponse(new AsyncCallback(WebClient.DownloadBitsResponseCallback), state);
return null;
}
response = this.m_WebResponse = this.GetWebResponse(request);
int bytesRetrieved = state.SetResponse(response);
while (!state.RetrieveBytes(ref bytesRetrieved))
{
}
state.Close();
return state.InnerBuffer;
}
So, I set up two breakpoints in Visual Studio:
1) One on the Sytem.Net.WebClient.DownloadBits method; and the other
2) On the System.Net.WebRequest.BeginGetResponse method.
I double-checked the following.
1) That I configured the Debugging settings in the Visual Studio Tools -> Options dialog correctly allowing the debugger to step through .NET framework source.
2) That I had enabled the downloading and caching of debug symbols to a proper location.
3) I double-checked the location and saw that there were Debug symbols for all the assemblies my code referenced and particularly for the System.dll which had the methods that my breakpoints were set on.
However, when I ran the code with debugging on, it complained that it couldn't find the debug symbols for System.dll. So, I clicked the Load button to let it download them at runtime from the Microsoft Symbol Server.
Even then, while it did break at the DownloadBits method, as I saw from the Call Stack Window and from the message it printed in the Output Window that I had asked it to print while setting up the breakpoint, it did not show or step into the source of that method.
I right-clicked the stack-frame of the DownloadBits method in the Call Stack Window to click the Load Symbols menu item, but it wasn't there. Consequently, the Go to Source Code menu item was also disabled.
I cleared the cache and let it download all assemblies afresh but that hasn't helped either.
I am using Visual Studio Community Edition 2015 and my program is targeting v4.5.2 of the .NET framework and I have previously been able to step into .NET source assemblies using this set up many times.
What have I been missing?
