blocks|key|2157581|text|您试过使用SendKeys类吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2157582|public+static+Image+TakeScreenSnapshot(bool+activeWindowOnly)
{
++++//+PrtSc+=+Print+Screen+Key
++++string+keys+=+"{PrtSc}";
++++if+(activeWindowOnly)
++++++++keys+=+"%25"+%2B+keys;+//+%25+=+Alt
++++SendKeys.SendWait(keys);
++++return+Clipboard.GetImage();
}|code-block|syntax|javascript|2157583|代码样本的来源|2157584|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.windows.forms.sendkeys.aspx|1|http://justlikeamagic.com/2009/04/13/programmatically-taking-a-screen-snapshot/^0|5|8|0|0|0|0|7|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@$A|10|B|11|1|12]]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

Have you tried using the <a href="http://msdn.microsoft.com/en-us/library/system.windows.forms.sendkeys.aspx" rel="nofollow">SendKeys</a> class instead?

<pre><code>public static Image TakeScreenSnapshot(bool activeWindowOnly)
{
 // PrtSc = Print Screen Key
 string keys = "{PrtSc}";
 if (activeWindowOnly)
 keys = "%" + keys; // % = Alt
 SendKeys.SendWait(keys);
 return Clipboard.GetImage();
}
</code></pre>

<a href="http://justlikeamagic.com/2009/04/13/programmatically-taking-a-screen-snapshot/" rel="nofollow">Source of code sample</a>

blocks|key|117002|text|public+const+int+KEYEVENTF_EXTENDEDKEY=0x0001;+//key+down
public+const+int+KEYEVENTF_KEYUP=0x0002;+//key+up|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|117003|但你用的是：|unstyled|117004|keybd_event(VK_SNAPSHOT,0,KEYEVENT_EXTENDEDKEY,0);
keybd_event(VK_SNAPSHOT,0,KEYEVENT_KEYUP,0);|117005|使用KEYEVENTF_EXTENDEDKEY和KEYEVENTF_KEYUP它可以工作|117006|整个过程运行在线程池上的一个工作线程中，我找不到将PrintScreen()发布到'Main-SynchronizationContext‘的方法，因为它是一个控制台程序。|117007|你可以试试这个：|117008|class+Program
{++++++++
++++[System.Runtime.InteropServices.DllImport("user32.dll")]
++++public+static+extern+void+keybd_event(byte+vVK,+byte+bScan,+int+dwFlags,+int+dwExtraInfo);

++++public+const+int+KEYEVENTF_EXTENDEDKEY+=+0x0001;+//key+down
++++public+const+int+KEYEVENTF_KEYUP+=+0x0002;+//key+up

++++public+const+int+VK_SNAPSHOT+=+0x2C;+//VirtualKey+code+for+print+key

++++public+static+void+PrintScreen()
++++{
++++++++keybd_event(VK_SNAPSHOT,+0,+KEYEVENTF_EXTENDEDKEY,+0);
++++++++keybd_event(VK_SNAPSHOT,+0,+KEYEVENTF_KEYUP,+0);
++++}

++++public+static+void+test(Action<Image>+action)
++++{
++++++++PrintScreen();
++++++++var+image+=+Clipboard.GetImage();
++++++++action.BeginInvoke(image,+ar+=>+action.EndInvoke(ar),+null);
++++}

++++[STAThread]
++++static+void+Main(string[]+args)
++++{
++++++++var+processAction+=+new+Action<Image>(img+=>
++++++++{
++++++++++++if+(img+==+null)
++++++++++++++++Console.WriteLine("none");
++++++++++++else
++++++++++++++++Console.WriteLine(img.PixelFormat);
++++++++});
++++++++test(processAction);
++++++++System.Console.ReadLine();
}|117009|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|T|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$B|C]]|$1|I|3|J|5|F|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$B|C]]|$1|Q|3|-4|5|F|7|Z|8|@]|9|@]|A|$]]]|R|$]]

<pre><code>public const int KEYEVENTF_EXTENDEDKEY=0x0001; //key down
public const int KEYEVENTF_KEYUP=0x0002; //key up
</code></pre>

but you are using:

<pre><code>keybd_event(VK_SNAPSHOT,0,KEYEVENT_EXTENDEDKEY,0);
keybd_event(VK_SNAPSHOT,0,KEYEVENT_KEYUP,0);
</code></pre>

use KEYEVENTF_EXTENDEDKEY and KEYEVENTF_KEYUP it works

<hr>

re: whole thing runs in a worker thread on the threadpool
I can't find a way to POST PrintScreen() To 'Main-SynchronizationContext', because it is a console program

you can try this:

<pre><code>class Program
{ 
 [System.Runtime.InteropServices.DllImport("user32.dll")]
 public static extern void keybd_event(byte vVK, byte bScan, int dwFlags, int dwExtraInfo);

 public const int KEYEVENTF_EXTENDEDKEY = 0x0001; //key down
 public const int KEYEVENTF_KEYUP = 0x0002; //key up

 public const int VK_SNAPSHOT = 0x2C; //VirtualKey code for print key

 public static void PrintScreen()
 {
 keybd_event(VK_SNAPSHOT, 0, KEYEVENTF_EXTENDEDKEY, 0);
 keybd_event(VK_SNAPSHOT, 0, KEYEVENTF_KEYUP, 0);
 }

 public static void test(Action&lt;Image&gt; action)
 {
 PrintScreen();
 var image = Clipboard.GetImage();
 action.BeginInvoke(image, ar =&gt; action.EndInvoke(ar), null);
 }

 [STAThread]
 static void Main(string[] args)
 {
 var processAction = new Action&lt;Image&gt;(img =&gt;
 {
 if (img == null)
 Console.WriteLine("none");
 else
 Console.WriteLine(img.PixelFormat);
 });
 test(processAction);
 System.Console.ReadLine();
}
</code></pre>

blocks|key|2157602|text|这是一个控制台程序|type|blockquote|depth|inlineStyleRanges|entityRanges|data|2157603|这是最相关的细节，你应该把它写在你的问题上。剪贴板是一个系统对象，其底层api是基于COM的。这使得它对使用api的线程的单元状态很敏感。.NET剪贴板类有一点错误，如果线程的状态是错误的，它应该会抛出异常。在控制台模式应用程序中，它是错误的，它的主线程默认是MTA，您需要STA来使用api。|unstyled|2157604|修复很简单，您可以在Main()方法上放置一个属性来请求STA：|2157605|++++[STAThread]
++++static+void+Main(string[]+args)+{
++++++++//+etc...
++++}|code-block|syntax|javascript|2157606|从技术上讲，STA线程也应该像Winforms或WPF应用程序那样，提供一个消息循环。但是，只要只从主线程发出方法调用，就可以逃脱它。|2157607|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Q|8|@]|9|@]|A|$]]|$1|E|3|F|5|D|7|R|8|@]|9|@]|A|$]]|$1|G|3|H|5|I|7|S|8|@]|9|@]|A|$J|K]]|$1|L|3|M|5|D|7|T|8|@]|9|@]|A|$]]|$1|N|3|-4|5|D|7|U|8|@]|9|@]|A|$]]]|O|$]]

<blockquote>
 It is a console program
</blockquote>

That's the most relevant detail, you should put it in your question. The Clipboard is a system object whose underlying api is COM based. Which makes it sensitive to the apartment state of the thread that uses the api. The .NET Clipboard class fumbles this a bit, it should really throw an exception if the thread's state is wrong. And it is wrong in the case of console mode app, its main thread is MTA by default and you need STA to use the api.

The fix is simple, you can just put an attribute on the Main() method to ask for STA:

<pre><code> [STAThread]
 static void Main(string[] args) {
 // etc...
 }
</code></pre>

Technically an STA thread should also pump a message loop, like a Winforms or WPF app does. But you'll get away with it as long as you only make the method calls from your main thread.

blocks|key|2157635|text|我知道这是一个更老的问题，但我想我会分享我的发现，因为它是与此相关的。我看到的问题是，只要代码中有断点，上面发布的方法就能工作。如果没有断点，事件就会触发，但只有在退出方法调用之后才会触发。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2157636|这意味着|2157637|++++InputController.PrintScreen();
++++var+img=Clipboard.GetImage();|code-block|syntax|javascript|2157638|因为剪贴板在离开这个方法之前是不会被填充的。这是一个使用DoEvents()的老VB技巧。这将允许我们的应用程序处理队列中的所有windows消息。因此，修改后的代码应该有效。|2157639|++++InputController.PrintScreen();
++++Application.DoEvents();
++++var+img=Clipboard.GetImage();|2157640|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I know this is an older question but I thought I would share my findings since it is related to this. The problem I was seeing was that the above posted methods worked as long as I had a breakpoint in the code. With no breakpoint the events would fire, but they would fire only after exiting the method call it was in.

This means something like 

<pre><code> InputController.PrintScreen();
 var img=Clipboard.GetImage();
</code></pre>

wont work because the Clipboard wont get populated until it leaves this method. The work around to this is an old VB trick using DoEvents(). This will allow our application to process all windows messages in the queue. So the revised code should work.

<pre><code> InputController.PrintScreen();
 Application.DoEvents();
 var img=Clipboard.GetImage();
</code></pre>

I am implementing different screen grabber to compare them. One of the should use the 'printscreen' key and the clipboard.

I send the keystroke with keybd_event:

<pre><code>[System.Runtime.InteropServices.DllImport("user32.dll")]
public static extern void keybd_event(byte vVK, byte bScan, int dwFlags,int dwExtraInfo);

public const int KEYEVENTF_EXTENDEDKEY=0x0001; //key down
public const int KEYEVENTF_KEYUP=0x0002; //key up

public const int VK_SNAPSHOT=0x2C; //VirtualKey code for print key

public static void PrintScreen(){
keybd_event(VK_SNAPSHOT,0,KEYEVENTF_EXTENDEDKEY,0);
keybd_event(VK_SNAPSHOT,0,KEYEVENTF_KEYUP,0);
}
</code></pre>

In my IEnumerable I call this method and try to grab the image afterwards:

<pre><code>...
InputController.PrintScreen();
var img=Clipboard.GetImage();
...
</code></pre>

The image returned is always null and Clipboards.ContainsImage() is false all the time. I´ve tried waiting a moment after sending the keys but it doesn´t work either.
Am I missing some kind of setup, or is there a fundamental error? 

PS: I am able to paste the correct image into paint or gimp after running the program.

No image in Clipboard after PrintScreen

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在实现不同的屏幕抓取来比较它们。其中一个应该使用“printscreen”键和剪贴板。我用keybd_event发送击键[System.Runtime.InteropServices.DllImport("user32.dll")]public static extern void keybd_event(byte...

问PrintScreen后剪贴板上没有图像
EN

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问PrintScreen后剪贴板上没有图像EN