c# - Create and Show a WinForm -

i´m trying create , show forms in vs 2013 generic method method:

void showorupdateform<t>(ref form form) t : form  {     if (form == null)     {         form = activator.createinstance(typeof(t)) t;         form.show();     }     else         form.windowstate = formwindowstate.normal;      form.focus(); } 

this code got here. when try call method told that:

 myform1 form;  showorupdateform<myform1>(ref form); 

it give me error:

error 1 best overloaded method match 'gestioneas.gestioneas.showorupdateform(ref system.windows.forms.form)' has invalid arguments

error 2 argument 1: cannot convert 'ref package.views.form' 'ref system.windows.forms.form'

how can fix this?

seems, want that:

// i'd rather return potentially created form directly (not via "ref") // need "this" in method? that's why "static" static t showorupdateform<t>(t form = null)   t: form, new() {    if (null == form)      form = new t(); // <- no activator since "new()" constraint declared    form.windowstate = formwindowstate.normal;   form.bringtofront(); // <- if form not foreground 1    if (form.canfocus) // <- better check have exception     form.focus();    return form; } ... // more compact , readable myform1 form = showorupdateform<myform1>();