Question

I had a button in first form .if i click the button the second form is opening ,if i click again same button in first form another second form is opening.i need to open only one second form only in c# .

Answer 1

Well you could do a :

Form.ShowDialog() 

This will prevent the user clicking the button on the first form, as the second form will keep focus until it is closed.

Or you could do

Form2 form2 = null;  void button_click(object sender, EventArgs e) {     if(form2 == null)    {       form2 = new Form2();       form2.Disposed += new EventHandler(f_Disposed);       form2.Show();    } }  void f_Disposed(object sender, EventArgs e) {    form2 = null; }