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  4. Illegal cross thread exception in Invoke method

Illegal cross thread exception in Invoke method

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  • A Abhinav S

    Try using BeginInvoke on your control instead.

    Me, I'm dishonest. And a dishonest man you can always trust to be dishonest.
    Honestly. It's the honest ones you want to watch out for...

    A Offline
    A Offline
    AspDotNetDev
    wrote on last edited by
    #7

    FYI, that would prevent a locking situation, but would not likely prevent a cross-thread exception. It would also change the flow of the program (i.e., the call would be asynchronous rather than blocking), which the OP may not want.

    [Forum Guidelines]

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    • A AspDotNetDev

      FYI, that would prevent a locking situation, but would not likely prevent a cross-thread exception. It would also change the flow of the program (i.e., the call would be asynchronous rather than blocking), which the OP may not want.

      [Forum Guidelines]

      L Offline
      L Offline
      Luc Pattyn
      wrote on last edited by
      #8

      I agree. :)

      Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

      I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.

      1 Reply Last reply
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      • A AspDotNetDev

        FYI, this is what code looks like when you wrap it in PRE tags and specify C# for the LANG attribute, as Luc mentioned:

        // Delegate:
        private delegate void ChangeTextDelegate(string text);

        // Method:
        public static void ChangeText(string text)
        {
        if (richtextbox1.InvokeRequired)
        {
        richtextbox1.Invoke(new ChangeTextDelegate(ChangeText), new object[] { text });
        }
        else
        {
        int startIndex;
        startIndex = richtextbox1.TextLength; // <- Exception points here.
        // ...
        }
        }

        Not sure why you are getting an exception there (perhaps post a screenshot and the full text of the exception?), but you might try the following to see if it works (changes in bold):

        // Delegate:
        private delegate void ChangeTextDelegate(string text);

        // Method:
        public static void ChangeText(string text)
        {
        if (this.InvokeRequired)
        {
        this.Invoke(new ChangeTextDelegate(ChangeText), new object[] { text });
        }
        else
        {
        int startIndex;
        startIndex = richtextbox1.TextLength; // <- Exception points here.
        // ...
        }
        }

        FYI, here is what I typed to make the code look like it does above:

        <pre lang="C#">// Delegate:
        private delegate void ChangeTextDelegate(string text);

        // Method:
        public static void ChangeText(string text)
        {
        if (<b><big><big><u>this</u></big></big></b>.InvokeRequired)
        {
        <b><big><big><u>this</u></big></big></b>.Invoke(new ChangeTextDelegate(ChangeText), new object[] { text });
        }
        else
        {
        int startIndex;
        startIndex = richtextbox1.TextLength; // <- Exception points here.
        // ...
        }
        }</pre>

        [Forum Guidelines]

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        Y Offline
        yeah1000
        wrote on last edited by
        #9

        Here is the stack trace, perhaps it can help clarify the problem...

        System.InvalidOperationException was unhandled
        Message="Cross-thread operation not valid: Control 'SomeClass' accessed from a thread other than the thread it was created on."
        Source="System.Windows.Forms"
        StackTrace:
        at System.Windows.Forms.Control.get_Handle()
        at System.Windows.Forms.Control.get_InternalHandle()
        at System.Windows.Forms.Control.WmWindowPosChanged(Message& m)
        at System.Windows.Forms.Control.WndProc(Message& m)
        at System.Windows.Forms.TextBoxBase.WndProc(Message& m)
        at System.Windows.Forms.RichTextBox.WndProc(Message& m)
        at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
        at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
        at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
        at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
        at System.Windows.Forms.NativeWindow.DefWndProc(Message& m)
        at System.Windows.Forms.Control.DefWndProc(Message& m)
        at System.Windows.Forms.Control.WmCreate(Message& m)
        at System.Windows.Forms.Control.WndProc(Message& m)
        at System.Windows.Forms.TextBoxBase.WndProc(Message& m)
        at System.Windows.Forms.RichTextBox.WndProc(Message& m)
        at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
        at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
        at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
        at System.Windows.Forms.UnsafeNativeMethods.IntCreateWindowEx(Int32 dwExStyle, String lpszClassName, String lpszWindowName, Int32 style, Int32 x, Int32 y, Int32 width, Int32 height, HandleRef hWndParent, HandleRef hMenu, HandleRef hInst, Object pvParam)
        at System.Windows.Forms.UnsafeNativeMethods.CreateWindowEx(Int32 dwExStyle, String lpszClassName, String lpszWindowName, Int32 style, Int32 x, Int32 y, Int32 width, Int32 height, HandleRef hWndParent, HandleRef hMenu, HandleRef hInst, Object pvParam)
        at System.Windows.Forms.NativeWindow.CreateHandle(CreateParams cp)
        at System.Windows.Forms.Control.CreateHandle()
        at System.Windows.Forms.TextBoxBase.CreateHandle()
        at System.Windows.Forms.Control.get_Handle()
        at System.Windows.Forms.Ric

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        • A AspDotNetDev

          FYI, this is what code looks like when you wrap it in PRE tags and specify C# for the LANG attribute, as Luc mentioned:

          // Delegate:
          private delegate void ChangeTextDelegate(string text);

          // Method:
          public static void ChangeText(string text)
          {
          if (richtextbox1.InvokeRequired)
          {
          richtextbox1.Invoke(new ChangeTextDelegate(ChangeText), new object[] { text });
          }
          else
          {
          int startIndex;
          startIndex = richtextbox1.TextLength; // <- Exception points here.
          // ...
          }
          }

          Not sure why you are getting an exception there (perhaps post a screenshot and the full text of the exception?), but you might try the following to see if it works (changes in bold):

          // Delegate:
          private delegate void ChangeTextDelegate(string text);

          // Method:
          public static void ChangeText(string text)
          {
          if (this.InvokeRequired)
          {
          this.Invoke(new ChangeTextDelegate(ChangeText), new object[] { text });
          }
          else
          {
          int startIndex;
          startIndex = richtextbox1.TextLength; // <- Exception points here.
          // ...
          }
          }

          FYI, here is what I typed to make the code look like it does above:

          <pre lang="C#">// Delegate:
          private delegate void ChangeTextDelegate(string text);

          // Method:
          public static void ChangeText(string text)
          {
          if (<b><big><big><u>this</u></big></big></b>.InvokeRequired)
          {
          <b><big><big><u>this</u></big></big></b>.Invoke(new ChangeTextDelegate(ChangeText), new object[] { text });
          }
          else
          {
          int startIndex;
          startIndex = richtextbox1.TextLength; // <- Exception points here.
          // ...
          }
          }</pre>

          [Forum Guidelines]

          Y Offline
          Y Offline
          yeah1000
          wrote on last edited by
          #10

          Soo, any ideas? :)

          A 1 Reply Last reply
          0
          • Y yeah1000

            Soo, any ideas? :)

            A Offline
            A Offline
            AspDotNetDev
            wrote on last edited by
            #11

            I assume you already tried using the "this" keyword like I said above? If that doesn't work, you can take two approaches. With one approach, try to create the error with a very small tester form. Then, post that here for us to review. Or, try removing code from your project little by little until it starts working.

            [Forum Guidelines]

            Y 1 Reply Last reply
            0
            • A AspDotNetDev

              I assume you already tried using the "this" keyword like I said above? If that doesn't work, you can take two approaches. With one approach, try to create the error with a very small tester form. Then, post that here for us to review. Or, try removing code from your project little by little until it starts working.

              [Forum Guidelines]

              Y Offline
              Y Offline
              yeah1000
              wrote on last edited by
              #12

              I am currently testing it with the 'this' keyword. But why should this approach solve the problem? What are the technicalities behind it? :)

              A 1 Reply Last reply
              0
              • Y yeah1000

                I am currently testing it with the 'this' keyword. But why should this approach solve the problem? What are the technicalities behind it? :)

                A Offline
                A Offline
                AspDotNetDev
                wrote on last edited by
                #13

                Was just a wild guess really. Not sure if it would help.

                [Forum Guidelines]

                Y 1 Reply Last reply
                0
                • A AspDotNetDev

                  Was just a wild guess really. Not sure if it would help.

                  [Forum Guidelines]

                  Y Offline
                  Y Offline
                  yeah1000
                  wrote on last edited by
                  #14

                  Okay, that didn't help :( Any more ideas?

                  A 1 Reply Last reply
                  0
                  • Y yeah1000

                    Okay, that didn't help :( Any more ideas?

                    A Offline
                    A Offline
                    AspDotNetDev
                    wrote on last edited by
                    #15

                    Show me the exact code that causes the problem. Create as small of a tester application as you can and paste ALL of the code for it (but remember to try and make the example concise). It's probably something simple, but I can't help you unless I see the code you are using.

                    [Forum Guidelines]

                    Y 1 Reply Last reply
                    0
                    • A AspDotNetDev

                      Show me the exact code that causes the problem. Create as small of a tester application as you can and paste ALL of the code for it (but remember to try and make the example concise). It's probably something simple, but I can't help you unless I see the code you are using.

                      [Forum Guidelines]

                      Y Offline
                      Y Offline
                      yeah1000
                      wrote on last edited by
                      #16

                      I was finally able to fix the problem: Apparently the handle for the richtextbox did not exist when i tried to invoke it. Since i used it in a background thread, the invokerequired property returned 'false', sometimes causing it to display the illegal cross thread operation exception (suring program startup). The solution was to use the Form_load event which would signal the background thread when it was fully loaded. But its still a bit unclear how such a thing can happen. When does actually InitializeComponent return? When can i be sure that the control handles exist?

                      A 1 Reply Last reply
                      0
                      • Y yeah1000

                        I was finally able to fix the problem: Apparently the handle for the richtextbox did not exist when i tried to invoke it. Since i used it in a background thread, the invokerequired property returned 'false', sometimes causing it to display the illegal cross thread operation exception (suring program startup). The solution was to use the Form_load event which would signal the background thread when it was fully loaded. But its still a bit unclear how such a thing can happen. When does actually InitializeComponent return? When can i be sure that the control handles exist?

                        A Offline
                        A Offline
                        AspDotNetDev
                        wrote on last edited by
                        #17

                        Glad to hear you got it working. :) InitializeComponent should be called from the constructor. You should only reference controls after that call to InitializeComponent.

                        [Forum Guidelines]

                        Y 1 Reply Last reply
                        0
                        • A AspDotNetDev

                          Glad to hear you got it working. :) InitializeComponent should be called from the constructor. You should only reference controls after that call to InitializeComponent.

                          [Forum Guidelines]

                          Y Offline
                          Y Offline
                          yeah1000
                          wrote on last edited by
                          #18

                          Oh but i did call it from the constructor, then started the background thread and inside that thread tried to access the controls.

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