Question

I have a winform with some buttons that are updated in an event handler. The event is fired from a background thread, then the appearance is set via the Invoke method. The buttons will just get enabled or disabled. Something will happen at unpredicable times, though:

• The button will not change appearance visually. When it should be enabled, it still looks like it’s disabled
• Clicking on the “disabled” button still fires the click event – as if its actually enabled underneath
• After resizing or moving the form, the component’s appearance is set correctly to enabled.
• Only the components that are updated in this manner are affected. Other components on the form look/behave fine.

Here is how the button is getting updated in code:

public class Form1 :Form
{
     void eventFromThread(object sender, CustomEventArgs e)
     {
           if(e.enable)   RunOnUiThread(ShowEnabledView);
           else RunOnUiThread(ShowDisabledView);
     }

     void ShowEnabledView()
     {
          button1.Enabled = true;
     }

     void ShowDisabledView()
     {
          button1.Enabled = false;
     }

     void RunOnUiThread(MethodInvoker method)
     {
          try
          {
                if(InvokeRequired)
                {
                     Invoke(method); 
                }
                else
                     method.Invoke();
           }
           catch(ObjectDisposedException)
           { return;}
           catch(InvalidOperationException)
            {return;}
     }
}

I have tried forcing a refresh on the button, and it hasn’t re-occurred yet, but its only been a couple of days. The issue just seems to pop up when it wants to, so I can’t really be sure I’m fixing anything. Can anyone shed any light on this?

Answer 1

try calling

System.Windows.Forms.Application.DoEvents()

after you change the button’s Enabled property