System.Windows.Forms.ContextMenu contextMenu1;
contextMenu1 = new System.Windows.Forms.ContextMenu();
System.Windows.Forms.MenuItem menuItem1;
menuItem1 = new System.Windows.Forms.MenuItem();
System.Windows.Forms.MenuItem menuItem2;
menuItem2 = new System.Windows.Forms.MenuItem();
System.Windows.Forms.MenuItem menuItem3;
menuItem3 = new System.Windows.Forms.MenuItem();

contextMenu1.MenuItems.AddRange(new System.Windows.Forms.MenuItem[] {menuItem1, menuItem2, menuItem3});
menuItem1.Index = 0;
menuItem1.Text = "MenuItem1";
menuItem2.Index = 1;
menuItem2.Text = "MenuItem2";
menuItem3.Index = 2;
menuItem3.Text = "MenuItem3";

textBox1.ContextMenu = contextMenu1;