Hi Narendra,
I could not understand your requirement clearly. If you want to enable docking for form using docking manager, I assume that you have set form''s Toplevel property to false and FormBorderstyle to None. as shown below,
this.f=new Form2();
this.f.TopLevel = false;
this.f.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
this.dockingManager1.SetEnableDocking(this.f,true);
Refer the following KB article:
How to dock a form?.
I am afraid I could not reproduce your mentioned problem. Could you please send me a sample which reproduces the issue?
Regards,
Vijay