Disabling Close Button in window form is much pretty easy.
First import the below namespace to resolve DllImport class.
using System.Runtime.InteropServices;
Write the below line of code on Form Load event.
//Disable Close Button-----------Start Here IntPtr hWnd = SystemMenuList(this.Handle, false); int nPosition = MenuItemCount(hWnd); const int wFlag = 0x400; RemoveMenu(hMenu, nPosition - 1, wFlag); //Disable Close Button-----------End Here
Add below methods to your form.
#region Disable Close Button [DllImport("User32")] private static extern IntPtr SystemMenuList(IntPtr hWnd, bool bRevert); [DllImport("User32")] private static extern int MenuItemCount(IntPtr hWnd); [DllImport("User32")] private static extern int RemoveMenu(IntPtr hMenu, int nPosition, int wFlag); #endregion