how can i reopen only 1 time a form?

The problem is solved with procesos.IsDisposed method: private void button2_Click(object sender, System.EventArgs e) { if (procesos==null || procesos.IsDisposed) { procesos=new frmProcesos(); procesos.Visible=true; } } Thanks

Could you paste in some more code so we can see where exactly the problem is? If you say that "frm never is run" that means the expression within the if statement is evaluated as false which leads to the conclusion that frm is previously assigned another value than null.

but this not run, frm never is run :(

make a form level variable to hold the form then assing the form to this and each time ur about to open it, check to see if its null