C# 使用WinApi操作剪切板Clipboard

前言：

最近正好写一个程序，需要操作剪切板

功能很简单，只需要从剪切板内读取字符串，然后清空剪切板，然后再把字符串导入剪切板

我想当然的使用我最拿手的C#来完成这项工作，原因无他，因为.Net框架封装了能实现这种功能的方法

然后就有了如下代码

             string Temp = "";
             while (true)
             {
                 string Tex = Clipboard.GetText().ToString();
                 if (!string.IsNullOrWhiteSpace(Tex) && Temp != Tex)
                 {
                     Clipboard.Clear();
                     Clipboard.SetDataObject(Tex, false);
                     Temp = Tex;
                 }
                 Thread.Sleep();
             }

这段代码，也是网页上广泛流传的，使用.Net框架操作系统剪切板的方法，当然这个方法在某些情况下很管用

不过在我这确发生了点问题，主要的问题有两点

首先，我对剪切板的操作需求有实时性，也就是，操作人员复制的一瞬间就应该截取到剪切板的数据，处理完后再放入剪切板

结果

 Clipboard.SetDataObject(Tex, false);

没想到上面这条设置剪切板的指令竟然会卡焦点窗口的线程，比如说，我在A软件执行了一次复制操作，如果使用了上述代码，那么A软件强制线程堵塞大概几百毫秒的样子，反正很影响体验，我推测是因为该命令会锁定内存导致的

那怎么办，本着死马当活马医的态度，我专门为该指令启用了一个线程

       Task.Factory.StartNew(()=>
                    {
                        Clipboard.Clear();
                        Clipboard.SetDataObject(Text, false);
                    });

使用了线程以后，因为操作滞后(线程启动会延迟一会儿，并不实时)了，所以上述问题似乎解决了，但是没想到出现了新的问题

 string Tex = Clipboard.GetText().ToString();

上述从剪切板获得字符串的指令，在默写情况下，会卡滞住，然后程序在一分钟之后，因为超时而被系统吊销

emmmmm，在经过几番努力之后，我终于意识到，虽然.Net封装了不少操作系统API的方法，使得一些IO操作变简单不少，但是带来的问题也是同样大的，在遇到无法解决的问题的时候，会有点束手无策

于是不得已，我只能放弃使用过C#完成该项功能，想着幸好功能简单，而且操作WinAPI其实最好的还是使用C++来写，于是我用C++复现了上述功能

 #include "stdafx.h"
 #include <windows.h>
 #include <iostream>
 using namespace std;
 #pragma comment(linker,"/subsystem:windows /entry:mainCRTStartup")

 int main(int argc, _TCHAR* argv[])
 {
     HANDLE THandle = GlobalAlloc(GMEM_FIXED, );//分配内存
     char* Temp = (char*)THandle;//锁定内存，返回申请内存的首地址
     while (true)
     {
         HWND hWnd = NULL;
         OpenClipboard(hWnd);//打开剪切板
         if (IsClipboardFormatAvailable(CF_TEXT))
         {
             HANDLE h = GetClipboardData(CF_TEXT);//获取剪切板数据
             char* p = (char*)GlobalLock(h);
             GlobalUnlock(h);
             if (strcmp(Temp, p))
             {
                 EmptyClipboard();//清空剪切板
                 HANDLE hHandle = GlobalAlloc(GMEM_FIXED, );//分配内存
                 char* pData = (char*)GlobalLock(hHandle);//锁定内存，返回申请内存的首地址
                 strcpy(pData, p);
                 strcpy(Temp, p);
                 SetClipboardData(CF_TEXT, hHandle);//设置剪切板数据
                 GlobalUnlock(hHandle);//解除锁定
             }
         }
         CloseClipboard();//关闭剪切板
         Sleep();
     }
     return ;
 }

不愧是C++，使用上述代码后，完美实现我需要的功能，而且不管是主程序，还是我写的这个程序，都不会出现卡滞或者不工作的情况了，真是可喜可贺。

那么本教程就到此为止。

以下是正文

想着，既然我能用C++调用WinAPI完美实现我需要的功能，而且C#也能调用非托管的代码来执行WinAPI，那么我不是可以把上面C++写的代码移植到C#里面执行？说干就干

首先，C#调用WinAPI需要先申明

        [DllImport("User32")]
        internal static extern bool OpenClipboard(IntPtr hWndNewOwner);

        [DllImport("User32")]
        internal static extern bool CloseClipboard();

        [DllImport("User32")]
        internal static extern bool EmptyClipboard();

        [DllImport("User32")]
        internal static extern bool IsClipboardFormatAvailable(int format);

        [DllImport("User32")]
        internal static extern IntPtr GetClipboardData(int uFormat);

        [DllImport("User32", CharSet = CharSet.Unicode)]
        internal static extern IntPtr SetClipboardData(int uFormat, IntPtr hMem);

操作剪切板需要调用的API大致就上面这些

有了API以后，我们还需要自己手动封装方法

     internal static void SetText(string text)
        {
            if (!OpenClipboard(IntPtr.Zero))
　　　　　　　　{
　　　　　　　　SetText(text);
　　　　　　　　return;
　　　　　　　　}
            EmptyClipboard();
            SetClipboardData(, Marshal.StringToHGlobalUni(text));
            CloseClipboard();
        }

        internal static string GetText(int format)
        {
            string value = string.Empty;
            OpenClipboard(IntPtr.Zero);
            if (IsClipboardFormatAvailable(format))
            {
                IntPtr ptr = NativeMethods.GetClipboardData(format);
                if (ptr != IntPtr.Zero)
                {
                    value = Marshal.PtrToStringUni(ptr);
                }
            }
            CloseClipboard();
            return value;
        }

我们也就用到两个方法，从剪切板获得文本和设置文本到剪切板，哦关于SetClipboardData的第一个参数13是怎么来的问题，其实这个剪切板的格式参数，下面有一张表，就是自从这里来的

public static class ClipboardFormat
{
    /// <summary>
    /// Text format. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character signals
    /// the end of the data. Use this format for ANSI text.
    /// </summary>
    public const int CF_TEXT = ;

    /// <summary>
    /// A handle to a bitmap (<c>HBITMAP</c>).
    /// </summary>
    public const int CF_BITMAP = ;

    /// <summary>
    /// Handle to a metafile picture format as defined by the <c>METAFILEPICT</c> structure. When passing a
    /// <c>CF_METAFILEPICT</c> handle by means of DDE, the application responsible for deleting <c>hMem</c> should
    /// also free the metafile referred to by the <c>CF_METAFILEPICT</c> handle.
    /// </summary>
    public const int CF_METAFILEPICT = ;

    /// <summary>
    /// Microsoft Symbolic Link (SYLK) format.
    /// </summary>
    public const int CF_SYLK = ;

    /// <summary>
    /// Software Arts' Data Interchange Format.
    /// </summary>
    public const int CF_DIF = ;

    /// <summary>
    /// Tagged-image file format.
    /// </summary>
    public const int CF_TIFF = ;

    /// <summary>
    /// Text format containing characters in the OEM character set. Each line ends with a carriage return/linefeed
    /// (CR-LF) combination. A null character signals the end of the data.
    /// </summary>
    public const int CF_OEMTEXT = ;

    /// <summary>
    /// A memory object containing a <c>BITMAPINFO</c> structure followed by the bitmap bits.
    /// </summary>
    public const int CF_DIB = ;

    /// <summary>
    /// Handle to a color palette. Whenever an application places data in the clipboard that depends on or assumes
    /// a color palette, it should place the palette on the clipboard as well. If the clipboard contains data in
    /// the <see cref="CF_PALETTE"/> (logical color palette) format, the application should use the
    /// <c>SelectPalette</c> and <c>RealizePalette</c> functions to realize (compare) any other data in the
    /// clipboard against that logical palette. When displaying clipboard data, the clipboard always uses as its
    /// current palette any object on the clipboard that is in the <c>CF_PALETTE</c> format.
    /// </summary>
    public const int CF_PALETTE = ;

    /// <summary>
    /// Data for the pen extensions to the Microsoft Windows for Pen Computing.
    /// </summary>
    public const int CF_PENDATA = ;

    /// <summary>
    /// Represents audio data more complex than can be represented in a CF_WAVE standard wave format.
    /// </summary>
    public const int CF_RIFF = ;

    /// <summary>
    /// Represents audio data in one of the standard wave formats, such as 11 kHz or 22 kHz PCM.
    /// </summary>
    public const int CF_WAVE = ;

    /// <summary>
    /// Unicode text format. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character
    /// signals the end of the data.
    /// </summary>
    public const int CF_UNICODETEXT = ;

    /// <summary>
    /// A handle to an enhanced metafile (<c>HENHMETAFILE</c>).
    /// </summary>
    public const int CF_ENHMETAFILE = ;

    /// <summary>
    /// A handle to type <c>HDROP</c> that identifies a list of files. An application can retrieve information
    /// about the files by passing the handle to the <c>DragQueryFile</c> function.
    /// </summary>
    public const int CF_HDROP = ;

    /// <summary>
    /// The data is a handle to the locale identifier associated with text in the clipboard. When you close the
    /// clipboard, if it contains <c>CF_TEXT</c> data but no <c>CF_LOCALE</c> data, the system automatically sets
    /// the <c>CF_LOCALE</c> format to the current input language. You can use the <c>CF_LOCALE</c> format to
    /// associate a different locale with the clipboard text.
    /// An application that pastes text from the clipboard can retrieve this format to determine which character
    /// set was used to generate the text.
    /// Note that the clipboard does not support plain text in multiple character sets. To achieve this, use a
    /// formatted text data type such as RTF instead.
    /// The system uses the code page associated with <c>CF_LOCALE</c> to implicitly convert from
    /// <see cref="CF_TEXT"/> to <see cref="CF_UNICODETEXT"/>. Therefore, the correct code page table is used for
    /// the conversion.
    /// </summary>
    public const int CF_LOCALE = ;

    /// <summary>
    /// A memory object containing a <c>BITMAPV5HEADER</c> structure followed by the bitmap color space
    /// information and the bitmap bits.
    /// </summary>
    public const int CF_DIBV5 = ;

    /// <summary>
    /// Owner-display format. The clipboard owner must display and update the clipboard viewer window, and receive
    /// the <see cref="ClipboardMessages.WM_ASKCBFORMATNAME"/>, <see cref="ClipboardMessages.WM_HSCROLLCLIPBOARD"/>,
    /// <see cref="ClipboardMessages.WM_PAINTCLIPBOARD"/>, <see cref="ClipboardMessages.WM_SIZECLIPBOARD"/>, and
    /// <see cref="ClipboardMessages.WM_VSCROLLCLIPBOARD"/> messages. The <c>hMem</c> parameter must be <c>null</c>.
    /// </summary>
    public const int CF_OWNERDISPLAY = 0x0080;

    /// <summary>
    /// Text display format associated with a private format. The <c>hMem</c> parameter must be a handle to data
    /// that can be displayed in text format in lieu of the privately formatted data.
    /// </summary>
    public const int CF_DSPTEXT = 0x0081;

    /// <summary>
    /// Bitmap display format associated with a private format. The <c>hMem</c> parameter must be a handle to
    /// data that can be displayed in bitmap format in lieu of the privately formatted data.
    /// </summary>
    public const int CF_DSPBITMAP = 0x0082;

    /// <summary>
    /// Metafile-picture display format associated with a private format. The <c>hMem</c> parameter must be a
    /// handle to data that can be displayed in metafile-picture format in lieu of the privately formatted data.
    /// </summary>
    public const int CF_DSPMETAFILEPICT = 0x0083;

    /// <summary>
    /// Enhanced metafile display format associated with a private format. The <c>hMem</c> parameter must be a
    /// handle to data that can be displayed in enhanced metafile format in lieu of the privately formatted data.
    /// </summary>
    public const int CF_DSPENHMETAFILE = 0x008E;

    /// <summary>
    /// Start of a range of integer values for application-defined GDI object clipboard formats. The end of the
    /// range is <see cref="CF_GDIOBJLAST"/>. Handles associated with clipboard formats in this range are not
    /// automatically deleted using the <c>GlobalFree</c> function when the clipboard is emptied. Also, when using
    /// values in this range, the <c>hMem</c> parameter is not a handle to a GDI object, but is a handle allocated
    /// by the <c>GlobalAlloc</c> function with the <c>GMEM_MOVEABLE</c> flag.
    /// </summary>
    public const int CF_GDIOBJFIRST = 0x0300;

    /// <summary>
    /// See <see cref="CF_GDIOBJFIRST"/>.
    /// </summary>
    public const int CF_GDIOBJLAST = 0x03FF;

    /// <summary>
    /// Start of a range of integer values for private clipboard formats. The range ends with
    /// <see cref="CF_PRIVATELAST"/>. Handles associated with private clipboard formats are not freed
    /// automatically; the clipboard owner must free such handles, typically in response to the
    /// <see cref="ClipboardMessages.WM_DESTROYCLIPBOARD"/> message.
    /// </summary>
    public const int CF_PRIVATEFIRST = 0x0200;

    /// <summary>
    /// See <see cref="CF_PRIVATEFIRST"/>.
    /// </summary>
    public const int CF_PRIVATELAST = 0x02FF;
}

在C++里面是不用指定数字的，只需要用CF_UNICODETEXT就行，不过.Net里面应该没有对应的索引表，所以只能手动输入(我这里是为了说明用才专门用数字，自己代码那是索引的枚举类)

上面两个工作做完以后，就能实现功能了，功能代码如下

                   var LastS = string.Empty;
                   while (!CancelInfoClipboard.IsCancellationRequested)
                   {
                       var Temp = ClipboardControl.GetText(ClipboardFormat.CF_UNICODETEXT);
                       if (!string.IsNullOrEmpty(Temp) && Temp != LastS)
                       {
                           ClipboardControl.SetText(Temp);
                           LastS = Temp;
                       }
                       Thread.Sleep();
                   }

是不是和最开始展示的调用.Net框架的方法一模一样(笑)，不过使用底层API实现的功能，就没有那么多乱七八糟的Bug了，自己也很清楚到底实现了啥功能，同时也收获了不少新知识(主要是非托管代码调用的时候的注意事项什么的，还有，向非托管代码传递数据的时候，最好多用Marshal类里面的方法，不然可能会出错，毕竟这个类就是专门为非托管代码而设立的)

接下来是新的发现

在研究MSDN上面关于剪切板的API的时候，发现了一个函数

bool AddClipboardFormatListener(HWND hwnd);

根据描述来讲，是添加一个剪切板的监控，在剪切板有任何变动的时候，通知你所指定的句柄的窗口，我一想，这不就是我所需要的么，有了这么一个API以后，其实我上面所展示的，使用死循环轮询剪切板的方法就变得很傻逼，而且也很容易出错了，于是，基于这个新发现的API，我重新更改了全部的程序逻辑，反而比原先的实现更加简单了。

首先我们需要一个新的窗口或者控件来接收Windows消息更新后所发来的消息，只要New 一个form就行

        public Form2()
        {
            InitializeComponent();
            AddClipboardFormatListener(this.Handle);
        }

然后我们在初始化组件的命令后面，把使用添加剪切板监听的API把当前窗口的句柄发给系统，这样系统在接收到剪切板改变的命令后，会把消息发给当前窗口

然后我们需要复写WndProc方法

   protected override void WndProc(ref Message m)
        {
            if (m.Msg == 0x031D && Onice)
            {var Temp = ClipboardControl.GetText(ClipboardFormat.CF_UNICODETEXT);
                    if (!string.IsNullOrEmpty(Temp))
                    {
                        ClipboardControl.SetText(Temp);
                        Onice = false;
                    }
            }
            else if (!Onice)
            {
                Onice = true;
            }
            else
            {
                base.WndProc(ref m);
            }
        }
   private bool Onice = true;

首先WndProc如果是Form类下面一个专门用来接收系统发送过来的消息的方法

然后关于m.Msg == 0x031D的0x031D在WinAPI定义上的意义是WM_CLIPBOARDUPDATE ，也就是剪切板更新事件，这个通过查找MSDN能够找到

下面没有特别奇怪的函数，就是有一点需要注意，我们这里设置了剪切板数据，相当于进行了一次更新，所以会在这一瞬间再次产生剪切板更新事件，然后又会通知这个方法，然后就会形成死循环，我在这里用了一个布尔判断来通过布尔状态决定是否截取剪切板，不只有有没有更好的办法来实现

以上