Form open more than 1 time c#

Check this links:

http://dotnetperls.com/single-instance-windows-form
http://www.megasolutions.net/cSharp/Single-Instance-Form-16441.aspx

Or google for Single Instance form in c#

If you are talking about the application in whole (main form) the following may help:
http://codebetter.com/blogs/paul.laudeman/archive/2004/07/17/Windows-Forms-Tip_3A00_-Ensure-only-one-instance-of-your-application-is-running-at-a-time.aspx

However, if you are talking about one of "secondary" forms, i.e. forms you are opening from your application, you may just check a reference to a form. You have to have an only variable to reference the form. If it is nothing - you create and open a new form. If not - show existing form.

This?

        public static void OpenForm(Type frmType)
        {
            bool bolCtl = false;
            foreach (Form form in Application.OpenForms)
            {
                if (form.GetType().Equals(frmType))
                {
                    form.Show();
                    bolCtl = true;
                    break;
                }
            }

            if (!bolCtl)
            {
                Form frm = (Form)Activator.CreateInstance(frmType);
                frm.Show();
            }
        }


        public static void LoadForm1()
        {
            OpenForm(typeof(Login));

            //Login _form1 = new Login();
            //_form1.Show();
        }

Hi,
Yes above both experts are right.