How to skip Validating after clicking on a Form's Cancel button

Question

I use C#. I have a Windows Form with an edit box and a Cancel button. The edit box has code in validating event. The code is executed every time the edit box loses focus. Wh

Answer 1

Maybe you want to use BackgroundWorker to give little bit delay, so you can decide whether validation should run or not. Here's the example of avoiding validation on form closing.

    // The flag
    private bool _isClosing = false;

    // Action that avoids validation
    protected override void OnClosing(CancelEventArgs e) {
        _isClosing = true;
        base.OnClosing(e);
    }

    // Validated event handler
    private void txtControlToValidate_Validated(object sender, EventArgs e) {           
        _isClosing = false;
        var worker = new BackgroundWorker();
        worker.DoWork += worker_DoWork;
        worker.RunWorkerAsync();
        worker.RunWorkerCompleted += worker_RunWorkerCompleted;
    }

    // Do validation on complete so you'll remain on same thread
    void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
        if (!_isClosing)
            DoValidationHere();
    }

    // Give a delay, I'm not sure this is necessary cause I tried to remove the Thread.Sleep and it was still working fine. 
    void worker_DoWork(object sender, DoWorkEventArgs e) {
        Thread.Sleep(100);
    }

Answer 2

In my case, in the form I set the property AutoValidate to EnableAllowFocusChange

Answer 3

In complement of the answer of Daniel Schaffer: if the validation occurs when the edit box loses focus, you can forbid the button to activate to bypass local validation and exit anyway.

public class UnselectableButton : Button
{
    public UnselectableButton()
    {
        this.SetStyle(ControlStyles.Selectable, false);
    }
}

or if you use DevExpress:

this.simpleButtonCancel.AllowFocus = false;

Note that doing so will change the keyboard experience: the tab will focus anymore on the cancel button.

Answer 4

Create a bool:

bool doOnce;

Set it to false in your function and then:

if (doOnce == false)
{
    e.cancel = true;
    doOnce = true;
}

This means it will only run once and you should be able to cancel it. This worked for me anyways.

Answer 5

Set the CausesValidation property of the Cancel button to false.