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I am developing a C# GUI-application using the Compact Framework for a Windows CE 5 scanner-device.

The application is used to repeatedly gather data entered by a user, mostly by a barcode scanner. there are two types of data: data that is only prompted at the beginning of a session (call it fixed-values) and data that is always shifting. the fixed-values can be changed by scanning some special barcodes, and this leads me to my problem:

The fixed-value data is entered in a dialog into ValidationTextBoxes (self-written class derived from TextBox). Until now, I called the dialog and presented all the fixed-value data to the user after he scanned the barcode for changing. If some data is invalid, an error message appears and the dialog can't be closed until the user enters valid data. I now got the task to don't show the dialog or hide it asap. I think it's not possible to change the data completely hidden and validate it without writing a new class for the validation (as it happens in a GUI-control), so I'd like to call the dialog with changed data, validate it, and if everything is OK, hide it. Otherwise keep it open as up to now.

The following method is called to show the dialog. If the "validate" flag is set, the data should be validated and if valid, the form should close.

Currently I am running into a ObjectDisposedException at "Control ctl = this.Controls[i];" in timer.Tick.

    public void display(List<InputRowDTO> fvList, bool validate)
    {
      this.fvList = fvList;
      ctlCount = (fvList.Count > 5 ? 5 : fvList.Count);
      for (int i = 0; i < ctlCount; i++)
      {
        // presenting the data
      }
      // adding some irrelevant eventhandlers

      if (validate)
      {
        System.Windows.Forms.Timer timer = new System.Windows.Forms.Timer();
        timer.Interval = 900;
        timer.Enabled = true;
        timer.Tick += (EventHandler)delegate(object obj, EventArgs args)
        {
          for (int i = 0; i < ctlCount; i++)
          {
            Control ctl = this.Controls[i]; // <- ObjectDisposedException
            bool valid = true;
            if (!((ValidationTextBox)ctl.Controls[1]).validate(((ValidationTextBox)ctl.Controls[1]).Text))
            {
              valid = false;
            }
            else if (((ValidationTextBox)ctl.Controls[1]).hasPrecepts())
            {
              if (!((ValidationTextBox)ctl.Controls[1]).validatePrecepts(((ValidationTextBox)ctl.Controls[1]).Text))
              {
                valid = false;
              }
            }
            if (validate && valid)
            {
              appendValuesAndClose();
            }
          }
          timer.Dispose();
        };
      }

      if (!this.Visible)
      {
        ShowDialog();
      }
    }

    private void appendValuesAndClose()
    {
      // get data out of the ValidationTextBoxes and write them to a controller, afterwards:
      this.Close();
    }
cutze
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  • Let the timer be part of your dialog, no? (or at least dispose it in your Dispose(bool) method). In that code it seems **you dispose** it after the **first tick**. Just disable it after the call to appendValuesAndClose() and let it be disposed where you dispose all other form objects. – Adriano Repetti Jun 21 '13 at 09:16
  • Yes, the timer shall dispose after the first tick, I just use it to delay the execution of appendValuesAndClose(). The ObjectDisposedException occurs while accessing controls of the Form, so I think the problem isn't the disposed Timer but the disposed Form. Or do I get that wrong? I'm usually coding in Java, so I'm not that familiar with C#... – cutze Jun 21 '13 at 09:19
  • Yes, easy to guess from "Java-ish" coding style! ;) Well, it depends where "ctl" is (not shown in code). If it comes from another (closed) dialog then it'll always fail because dialog has been disposed. – Adriano Repetti Jun 21 '13 at 09:27
  • Oh, sorry, I forgot to put that line into the code example! I just edited the code. Control ctl = this.Controls[i]; The for-loop in the Timer.Tick event iterates all the controls on the Form. What I try to achieve with the timer is to execute the loop after the Dialog is shown. – cutze Jun 21 '13 at 09:32
  • I would make the timer a private class member instead of a local variable (plus what I said about disposing). – Adriano Repetti Jun 21 '13 at 11:10
  • To take a different tact, ***don't*** put business logic in Forms. Are you really showing a form, briefly, just to run the business logic in it? Really? – tcarvin Jun 22 '13 at 20:42

0 Answers0