如何设置默认输入法为半角状态，

 [DllImport("imm32.dll")]
        public static extern IntPtr ImmGetContext(IntPtr hwnd);
        [DllImport("imm32.dll")]
        public static extern bool ImmGetOpenStatus(IntPtr himc);
        [DllImport("imm32.dll")]
        public static extern bool ImmSetOpenStatus(IntPtr himc, bool b);
        [DllImport("imm32.dll")]
        public static extern bool ImmGetConversionStatus(IntPtr himc, ref   int lpdw, ref   int lpdw2);
        [DllImport("imm32.dll")]
        public static extern int ImmSimulateHotKey(IntPtr hwnd, int lngHotkey);
        private const int IME_CMODE_FULLSHAPE = 0x8;
        private const int IME_CHOTKEY_SHAPE_TOGGLE = 0x11;
        protected override void OnActivated(EventArgs e)
        {
            base.OnActivated(e);
            IntPtr HIme = ImmGetContext(this.Handle);     
            if (ImmGetOpenStatus(HIme)) 
            {
                int iMode = 0;
                int iSentence = 0;
                bool bSuccess = ImmGetConversionStatus(HIme, ref   iMode, ref   iSentence);     
                if (bSuccess)
                {
                    if ((iMode & IME_CMODE_FULLSHAPE) > 0)        
                        ImmSimulateHotKey(this.Handle, IME_CHOTKEY_SHAPE_TOGGLE);        
                }            }
        }