Static variables generating problems with C# (Windows 8)

Question

I am not a used C# programmer, so if this is stupid, sorry :-)

I am developing a C# app for Windows 8. I need to do a web request, and therefore, I have a callback to handle the request data.

I am using the standard approach:

private static ManualResetEvent allDone = new ManualResetEvent(false);

private static void daCallback(IAsyncResult data) {
   ...
   SampleDataSource.allDone.Set();
}

// This is the Class CONSTRUCTOR
public SampleDataSource() {
   # before anything, reset allDone:

  string request = "http://some.url.com";
  HttpWebRequest webRequest = WebRequest.Create(request) as HttpWebRequest;
  webRequest.Method = "POST";

  webRequest.BeginGetResponse(new AsyncCallback(daCallback), webRequest);

  Debug.WriteLine("Asked to begin get response");

  SampleDataSource.allDone.WaitOne(12000);

  Debug.WriteLine("Done Waiting");
   #...
}

When running, allDone (inside do_something) is not initialized. I even added a condition around to compare allDone with null, and yep, it is null.

The "Done Waiting" message never gets print at all...

What am I doing wrong?

Thank you

Why do you need a reset event at all? (And are you sure some other code somewhere isn't setting it to null? From the code you've posted here it shouldn't be...) — Cameron, Nov 20 '12 at 19:43
@Cameron, it doesn't matter if I am calling Reset, or set, or WaitOne. It is not defined. Why? — Alberto, Nov 20 '12 at 19:44
@ambs perhaps you have some other variable/property etc. named allDone ? — Yahia, Nov 20 '12 at 19:45
@ambs then just reference it via `YourClassName.allDone` and see what happens... — Yahia, Nov 20 '12 at 19:46
@Yahia, tried it. I still get complains about NullReferenceException. Something weird here :-) — Alberto, Nov 20 '12 at 19:53
@ambs that contradicts what you showed as code... it is either a weird compiler/runtime issue OR some other (beside what you show) does something to produce this behaviour... I bet on the latter... — Yahia, Nov 20 '12 at 19:55
@Yahia, added some more code in the post, hopefully that can show some stupid error I am doing :-) — Alberto, Nov 20 '12 at 20:00
Fond out that WaitOne should receive a number of milliseconds for Windows 8 Store Apps... but still no fun. — Alberto, Nov 20 '12 at 20:50
Can't understand why, but initializing allDone in the method works (now that WaitOne has a timeout). But still, can't understand why it doesn't work as above. — Alberto, Nov 20 '12 at 20:54

score 2 · Answer 1 · answered Nov 20 '12 at 19:44

2

You're calling a static field from an instance method. Use YourClassName.allDone.Reset() instead.

answered Nov 20 '12 at 19:44

Dennis Traub

50,557
7
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score 2 · Answer 2 · answered Nov 20 '12 at 19:45

2

You have to add the classname in front of your call to allDone, because it's static. So instead of

allDone.Reset();

try

//replace CLASS with whatever you named your class
CLASS.allDone.Reset();

Equivalent approach to all other calls.

answered Nov 20 '12 at 19:45

KeyNone

8,745
4
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51

That would explain it all. But it seems it continues to be with a null value. – Alberto Nov 20 '12 at 19:48
@ambs Did you try setting a breakpoint at `private static ManualResetEvent allDone = new ManualResetEvent(false);`? This way you can be sure it really gets called or not (and that allDone isn't null afterwards). – KeyNone Nov 21 '12 at 07:40

Static variables generating problems with C# (Windows 8)

2 Answers2