code to create function in class file disable multiple panel

        void DisablePanels(Control container)

        {

            foreach (Control c in container.Controls)

            {

                if (c is Panel)

                {

                    c.Enabled = false;

                }

                else if (c.HasChildren)

                {

                    DisablePanels(c);

                }

            }

        }

If you're calling this method from within the form which contains the panels, then call with:

   DisablePanels(this);

If you're calling it from within some other form or class and you want to disable the panels on Form1 (say), then call with:

Form f1 = (Form1)Application.OpenForms["Form1"];
DisablePanels(f1);