winforms - Avoid duplicate form loading in c# -
i have 2 windows forms.both form1 , form2 have button. when click button in form1 shows form2 , vice versa. create duplicate form when click button on each time. how avoid it. please tell me. code given below. form1: private void button1_click(object sender, eventargs e) { form2 f2 = new form2(); f2.show(); } form2: private void button1_click(object sender, eventargs e) { form1 f1 = new form1(); f1.show(); } just use method common , pass parameter 'this' when button click public bool formisexist(form frmopen) { formcollection fc = application.openforms; foreach (form frm in fc) { if (frm.name == frmopen.name) { return true; } } return false; }