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
1 string Temp = ""; 2 while (true) 3 { 4 string Tex = Clipboard.GetText().ToString(); 5 if (!string.IsNullOrWhiteSpace(Tex) && Temp != Tex) 6 { 7 Clipboard.Clear(); 8 Clipboard.SetDataObject(Tex, false); 9 Temp = Tex; 10 } 11 Thread.Sleep(1); 12 }
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
1 #include "stdafx.h" 2 #include <windows.h> 3 #include <iostream> 4 using namespace std; 5 #pragma comment(linker,"/subsystem:windows /entry:mainCRTStartup") 6 7 int main(int argc, _TCHAR* argv[]) 8 { 9 HANDLE THandle = GlobalAlloc(GMEM_FIXED, 1000);//分配内存 10 char* Temp = (char*)THandle;//锁定内存，返回申请内存的首地址 11 while (true) 12 { 13 HWND hWnd = NULL; 14 OpenClipboard(hWnd);//打开剪切板 15 if (IsClipboardFormatAvailable(CF_TEXT)) 16 { 17 HANDLE h = GetClipboardData(CF_TEXT);//获取剪切板数据 18 char* p = (char*)GlobalLock(h); 19 GlobalUnlock(h); 20 if (strcmp(Temp, p)) 21 { 22 EmptyClipboard();//清空剪切板 23 HANDLE hHandle = GlobalAlloc(GMEM_FIXED, 1000);//分配内存 24 char* pData = (char*)GlobalLock(hHandle);//锁定内存，返回申请内存的首地址 25 strcpy(pData, p); 26 strcpy(Temp, p); 27 SetClipboardData(CF_TEXT, hHandle);//设置剪切板数据 28 GlobalUnlock(hHandle);//解除锁定 29 } 30 } 31 CloseClipboard();//关闭剪切板 32 Sleep(500); 33 } 34 return 0; 35 }
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(13, 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 = 1; /// <summary> /// A handle to a bitmap (<c>HBITMAP</c>). /// </summary> public const int CF_BITMAP = 2; /// <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 = 3; /// <summary> /// Microsoft Symbolic Link (SYLK) format. /// </summary> public const int CF_SYLK = 4; /// <summary> /// Software Arts' Data Interchange Format. /// </summary> public const int CF_DIF = 5; /// <summary> /// Tagged-image file format. /// </summary> public const int CF_TIFF = 6; /// <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 = 7; /// <summary> /// A memory object containing a <c>BITMAPINFO</c> structure followed by the bitmap bits. /// </summary> public const int CF_DIB = 8; /// <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 = 9; /// <summary> /// Data for the pen extensions to the Microsoft Windows for Pen Computing. /// </summary> public const int CF_PENDATA = 10; /// <summary> /// Represents audio data more complex than can be represented in a CF_WAVE standard wave format. /// </summary> public const int CF_RIFF = 11; /// <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 = 12; /// <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 = 13; /// <summary> /// A handle to an enhanced metafile (<c>HENHMETAFILE</c>). /// </summary> public const int CF_ENHMETAFILE = 14; /// <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 = 15; /// <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 = 16; /// <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 = 17; /// <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(50);
}
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
