Find the open forms in c# windows application

Question

I am using this function to close existing form and open a new form.

If there is no exixting form, it throws error.

Error :

Target : System.Object

Answer 1

If you know the name of the form you can as well do like this :

var frm = Application.OpenForms.Cast<Form>().Where(x => x.Name == "MyForm").FirstOrDefault();
if (null != frm)
{
    frm.Close();
    frm = null;
}

Answer 2

if (ApplicationFormStatus.CheckIfFormIsOpen("FormName")) 
{
// It means it exists, so close the form
}

 public bool CheckIfFormIsOpen(string formname)
        {

            //FormCollection fc = Application.OpenForms;
            //foreach (Form frm in fc)
            //{
            //    if (frm.Name == formname)
            //    {
            //        return true;
            //    }
            //}
            //return false;

            bool formOpen= Application.OpenForms.Cast<Form>().Any(form => form.Name == formname);

            return formOpen;
        }

I have pasted the two methods one simple one and the second one is the LINQ.

Answer 3

You can use the Application.OpenForms collection.

Answer 4

this part of code searches for existing instance of a form if exists just shows it , and if not creates an instance of it

       `foreach (Form form in Application.OpenForms)
        {
            if (form.GetType() == typeof(myMainform))
            {
                form.Activate();
                form.Show();
                this.Close();
                return;
            }
        }

        myMainform m = new myMainform();
        m.Show();`