MDI Parent form

Question

Form1 objForm1 = new Form1 ();
objForm1 .MdiParent = this;
objForm1 .Show();

This is my code to open MDI form . IF I open this page again, it appears again and again and so many windows opens. Can anybody help?

Answer 1

If you want to create a new form only if it is not already opened you can do this:

ShowFormIfNotOpen(this,typeof(Form1));

public static void ShowFormIfNotOpen(Form mainform,Type type)
    {
        foreach (Form item in mainform.MdiChildren)
            if (item.GetType() == type)
            {
                item.Activate();
                return;
            }

         Form form = Activator.CreateInstance(type) as Form;
        form.MdiParent = mainform;
        form.Show();
    }

Update

1)Add a public static bool field/property in your form (IsAlreadyShown)

public static bool IsAlreadyShown { get; set; }

2)Set it to true in the constructor of the form

public Form1()
{
     InitializeComponent();
     IsAlreadyShown = true;
 }

3)Call ShowForm1(this);

public static void ShowForm1(Form parentForm)
    {
        if(Form1.IsAlreadyShown ==true)
                return;


        Form1 objForm1 = new Form1 ();
        objForm1 .MdiParent = parentForm;
        objForm1 .Show();
    }