To check if a form is already running you’ll have to look for it in the Application.OpenForms collection. When a form is opened it is added to that collection.

Here’s a boolean method that checks whether a form is open or not :

private bool CheckForm(Form form)
{
   foreach (Form f in Application.OpenForms)
       if (form == f)
          return true;

 return false;
}

Example use:

// if form2 is not running

if (!CheckForm(form2))
  {
      // do something
  }

Thanks.

If you have any questions, don’t hesitate to post a comment.