how to pass form as a variable to function

Question

hello ..

i have a question ..

i am having mdi parent and at least 50 child forms in my application

now when create a function by passing "frmuser" as  user it gives me error..

but i want these all lines in a function, olz help me...

 

 if (Application.OpenForms.OfType<frmUser>().Count() >= 1)     

       {        

      Application.OpenForms.OfType<frmUser>().First().Activate();  

           }        

     else   

          {        

         frmUser u = new frmUser();     

            u.MdiParent = this;       

          u.Show();       

      }