原文:http://topic.csdn.net/u/20090218/12/1c2be55b-b894-4fc7-b99d-dd91f929dbc3.html?seed=168651165
最直接的方法就是打补丁:
http://download.csdn.net/source/320345
或者
https://files.cnblogs.com/zyh-nhy/vs2005输入法补丁.rar
下面的代码没有测试过,转载的:

Code
//声明一些API函数
[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;
//重载Form的OnActivated
protected override void OnActivated(EventArgs e)
{
base.OnActivated(e);
IntPtr HIme = ImmGetContext(this.Handle);
if (ImmGetOpenStatus(HIme)) //如果输入法处于打开状态
{
int iMode = 0;
int iSentence = 0;
bool bSuccess = ImmGetConversionStatus(HIme, ref iMode, ref iSentence); //检索输入法信息
if (bSuccess)
{
if ((iMode & IME_CMODE_FULLSHAPE) > 0) //如果是全角
ImmSimulateHotKey(this.Handle, IME_CHOTKEY_SHAPE_TOGGLE); //转换成半角
}
}
}