要設置快捷鍵必須使用user32.dll下面的兩個方法。
bool registerhotkey( //注冊系統熱鍵的api函數
　hwnd hwnd,
　int id,
　uint fsmodifiers,
　uint vk
);
 
bool unregisterhotkey( //刪除系統熱鍵的api函數
　hwnd hwnd,
　int id
);
 
在c#中引用命名空間system.runtime.interopservices;來加載非托管類user32.dll
using system;
using system.collections.generic;
using system.componentmodel;
using system.data;
using system.drawing;
using system.text;
using system.windows.forms;
 
namespace hotkey
{
 
    public enum keymodifiers //組合鍵枚舉
    {
        none = 0,
        alt = 1,
        control = 2,
        shift = 4,
        windows = 8
    }
 
    public partial class form1 : form
    {
        /*
         * registerhotkey函數原型及說明：
         * bool registerhotkey(
         * hwnd hwnd,         // window to receive hot-key notification
         * int id,            // identifier of hot key
         * uint fsmodifiers, // key-modifier flags
         * uint vk            // virtual-key code);
         * 參數 id為你自己定義的一個id值
         * 對一個線程來講其值必需在0x0000 - 0xbfff范圍之內,十進制為0~49151
         * 對dll來講其值必需在0xc000 - 0xffff 范圍之內,十進制為49152~65535
         * 在同一進程內該值必須唯一參數 fsmodifiers指明與熱鍵聯合使用按鍵
         * 可取值為：mod_alt mod_control mod_win mod_shift參數，或數字0為無，1為alt,2為control，4為shift，8為windows
         * vk指明熱鍵的虛擬鍵碼
         */
 
        [system.runtime.interopservices.dllimport("user32.dll")] //申明api函數
        public static extern bool registerhotkey(
         intptr hwnd, // handle to window
         int id, // hot key identifier
         uint fsmodifiers, // key-modifier options
         keys vk // virtual-key code
        );
        [system.runtime.interopservices.dllimport("user32.dll")] //申明api函數
        public static extern bool unregisterhotkey(
         intptr hwnd, // handle to window
         int id // hot key identifier
        );
        public form1()
        {
            initializecomponent();
        }
        private void processhotkey(message m) //按下設定的鍵時調用該函數
        {
            intptr id = m.wparam; //intptr用于表示指針或句柄的平臺特定類型
            //messagebox.show(id.tostring());
            string sid = id.tostring();
            switch (sid)
            {
                case "100":
                    messagebox.show("調用a函數");
                    break;
                case "200":
                    messagebox.show("調用b函數");
                    break;
            }
        }
        private void form1_load(object sender, eventargs e)
        {
            //handle為當前窗口的句柄,繼續自control.handle,control為定義控件的基類
            //registerhotkey(handle, 100, 0, keys.a); //注冊快捷鍵,熱鍵為a
            //registerhotkey(handle, 100, keymodifiers.alt | keymodifiers.control, keys.b);//這時熱鍵為alt+ctrl+b
            //registerhotkey(handle, 100, 1, keys.b); //1為alt鍵，熱鍵為alt+b
            registerhotkey(handle, 100, 2,keys.a); //定義熱鍵為alt+tab，這里實現了屏幕系統alt+tab鍵
            registerhotkey(handle, 200, 2, keys.b); //注冊2個熱鍵,根據id值100,200來判斷需要執行哪個函數
        }
 
        private void button1_click(object sender, eventargs e) //重新設置熱鍵
        {
            unregisterhotkey(handle, 100);//卸載快捷鍵
            registerhotkey(handle, 100, 2, keys.c); //注冊新的快捷鍵，參數0表示無組合鍵
        }
 
        private void form1_formclosing(object sender, formclosingeventargs e) //退出程序時缷載熱鍵
        {
            unregisterhotkey(handle, 100);//卸載第1個快捷鍵
            unregisterhotkey(handle, 200); //缷載第2個快捷鍵
        }
 
        //重寫wndproc()方法，通過監視系統消息，來調用過程
        protected override void wndproc(ref message m)//監視windows消息
        {
            const int wm_hotkey = 0x0312;//如果m.msg的值為0x0312那么表示用戶按下了熱鍵
            switch (m.msg)
            {
                case wm_hotkey:
                    processhotkey(m);//按下熱鍵時調用processhotkey()函數
                    break;
            }
            base.wndproc(ref m); //將系統消息傳遞自父類的wndproc
        }
    }
}