Object reference not set to an instance...

[JumpyNET]

I have an application which detects if an instance of it is allready running. And if so it will SendMessage(WM_SETTEXT) to the first instance's TextBox called communicator. This works correctly! But the problem is that I get an error in the TextChanged event:

 

       private void Communicator_TextChanged(object sender, EventArgs e)
       {
           String msg = Communicator.Text ;
           //MessageBox.Show(this,msg); 
           ActiveForm.Text = msg;
       }

 

The MessageBox (commented out) will show correctly but why doesn't it work without "this"?

 

The real problem is "ActiveForm.Text = msg;", which causes the following error: "Object reference not set to an instance of an object.".

[Machaira]

What's the Call Stack look like when it hits this line? Are you in the middle of destroying the ActiveForm?

[JumpyNET]

Call Stack

 

What's the Call Stack look like when it hits this line? Are you in the middle of destroying the ActiveForm?

 

Like this. I'm destroying the instance that sent the message but not the one receiving it.

[Machaira]

I'm assuming the exception is occurring in the second instance. How are you sending the message to the first instance?

[JumpyNET]

I'm assuming the exception is occurring in the second instance. How are you sending the message to the first instance?

 

 

SendMessage(ComHandle, WM_SETTEXT, 256, "Teksti");

 

ComHandle is read from a static place in windows registry were the first instance will save it's Communicator.Handle.