class TextBoxExt:TextBox

    {

        private const int WM_RBUTTONDOWN = 0x0204;

        private const int WM_CHAR = 0x0102;

        protected override void WndProc(ref Message m)

        {

            switch (m.Msg)

            {

                case WM_RBUTTONDOWN:

                    return;//屏蔽默认右键菜单

                    break;

                case WM_CHAR:

                    int n = (int)m.WParam;

                    if (n==)//允许输入退格键

                    {

                        base.WndProc(ref m);

                    }

                    if (n>= && n<=)//允许输入0-9

                    {

                        base.WndProc(ref m);

                    }

                    else

                    {

                        return;

                    }

                    break;

                default:

                    base.WndProc(ref m);

                    break;

            }

        }

    }