Ensuring that all callbacks were completed before sending a new request through a DuplexChannel usin
- by Etan
I am experiencing some issues when using a Callback in a WCF project.
First, the server invokes some function Foo on the client which then forwards the request to a Windows Forms GUI:
GUI CLASS
delegate void DoForward();
public void ForwardToGui() {
if (this.cmdSomeButton.InvokeRequired) {
DoForward d = new DoForward(ForwardToGui);
this.Invoke(d);
}
else {
Process(); // sets result variable in callback class as soon as done
}
}
}
CALLBACK CLASS
object _m = new object();
private int _result;
public int result {
get { return _result; }
set {
_result = value;
lock(_m) {
Monitor.PulseAll(_m);
}
}
}
[OperationContract]
public int Foo() {
result = 0;
Program.Gui.ForwardToGui();
lock(_m) {
Monitor.Wait(_m, 30000);
}
return result;
}
The problem now is that the user should be able to cancel the process, which doesn't work properly:
SERVER INTERFACE
[OperationContract]
void Cleanup();
GUI CLASS
private void Gui_FormClosed(object sender, EventArgs e) {
Program.callbackclass.nextAction = -1;
// so that the monitor pulses and Foo() returns
Program.server.Cleanup();
}
The problem with this is that Cleanup() hangs. However, when I close the form when Process() is not running, it works properly.
The source seems to be that the Cleanup() is called before the monitor pulses etc and therefore a new request is sent to the server before the last request from the server has not yet been responded.
How can I solve this problem? How can I ensure before calling Cleanup() that no Foo() is currently being executed?
