private void menuTrangChu_Click(object sender, EventArgs e)
 {
     if (!this.MdiChildren[0].Name.Equals("FormTrangChu"))
     {
         disposeAllMDIChildrenForms();
         FormTrangChu formTrangChu = new FormTrangChu();
         showFormInMDIContainer(formTrangChu);
     }
 }
        private void formMain_Load(object sender, EventArgs e)
        {
            FormTrangChu formTrangChu = new FormTrangChu();

            showFormInMDIContainer(formTrangChu);
        }