How to mark C# event handler as "handled"?

Question

Say I've got a button on a form that I want to disable if some condition is met. Is there a way to check for this condition inside the button's "IsEnabled" event handler and modify the enabled state such that setting the enabled state a second time does not trigger another call to the IsEnabled event handler?

Let me demonstrate:

private void ExportResults_IsEnabledChanged (object sender, DependencyPropertyChangedEventArgs e)
{
 if (some condition)
 {
  uxExportResults.IsEnabled = false; // this will cause another call to the event handler, eventually resulting in a stack overflow
 }
}

Assume I'm triggering the event elsewhere (which I am).

Answer 1

if (someCondition && uxExportResults.IsEnabled) { ... }

This will only disable your control if it's enabled.

Answer 2

Simplest solution is to check the value of IsEnabled before you set it.

private void ExportResults_IsEnabledChanged (object sender, DependencyPropertyChangedEventArgs e)
{
  if (uxExportResults.IsEnabled == true)
  {
    uxExportResults.IsEnabled = false;
  }
}

Also, if you have the ability to change the code for the button, IsEnabled should not send the event unless the value actually changes.

public bool IsEnabled
{
  get { return isEnabled; }
  set
  {
    if(isEnabled != value)
    {
      isEnabled = value;
      IsEnabledChanged(this,args);
    }
  }
}

Answer 3

Another option is to temporarily disable the event like so:

private void ExportResults_IsEnabledChanged (object sender, DependencyPropertyChangedEventArgs e)
{
    if (some condition)
    {
        uxExportResults.IsEnabledChanged -= ExportResults_IsEnabledChanged;
        try
        {
            uxExportResults.IsEnabled = false; // this will cause another call to the event handler, eventually resulting in a stack overflow
        }
        finally
        {
            uxExportResults.IsEnabledChanged += ExportResults_IsEnabledChanged;
        }
    }
}