1、命名空间：
using System.Runtime.InteropServices;
2、导入方法
[DllImport("user32.dll", EntryPoint = "GetKeyboardState")]
public static extern int GetKeyboardState(byte[] pbKeyState);
3、大小写状态
public static bool CapsLockStatus
{
get
{
byte[] bs = new byte[256];
GetKeyboardState(bs);
return (bs[0x14] == 1);
}
}
4、引用，此部分根据你的需要来修改
private void button2_Click(object sender, EventArgs e)
{
if (CapsLockStatus == true)
MessageBox.Show("键盘处于大写锁定状态！");
else
MessageBox.Show("键盘处于小写状态！");
}