这真的是一个非法的跨线程调用吗？ [英] Is this really an Illegal Cross Thread Call?
问题描述
我有一个Thread回调Form函数改变Form数据。
当然，调试器告诉我，跨线程操作无效：
控制''FormTest''从一个线程以外的线程访问
创建。
但我锁定之前我触摸共享数据，所以我真的需要担心这个，或者只是调试器过于简单？
具体来说，我有：
public delegate void TestEvent（ref string Payload）;
public class FormTest：System.Windows.Forms.Form
{
...
无效运行
{
TestHarness test = new TestHarness（）;
test.Callback + = TestFunction; //回调的类型是
TestEvent
线程t =新线程（新的ThreadStart（test.Go））;
t.IsBackground = true;
t.Start（）;
}
private void TestFunction（ref string Payload）
{
lock（this）WriteOut（ref Payload）; // ???这不是锁定
防止线程同步问题???
}
private void WriteOut（ref string Payload）
{
this.Text =有效载荷;
}
I have a Thread making a callback to a Form function that alters Form data.
Of course, the debugger is telling me, "Cross-thread operation not valid:
Control ''FormTest'' accessed from a thread other than the thread it was
created on."
But I am locking before I touch the shared data, so do I actually need to
worry about this, or is it just the debugger being oversimplistic?
Specifically, I have:
public delegate void TestEvent(ref string Payload);
public class FormTest : System.Windows.Forms.Form
{
...
void Run
{
TestHarness test = new TestHarness();
test.Callback += TestFunction; // Callback is of type
TestEvent
Thread t = new Thread(new ThreadStart(test.Go));
t.IsBackground = true;
t.Start();
}
private void TestFunction(ref string Payload)
{
lock(this) WriteOut(ref Payload); // ??? Doesn''t this lock
prevent thread synchronization problems???
}
private void WriteOut(ref string Payload)
{
this.Text = Payload;
}
推荐答案
Dave，
Dave,
但我在触摸共享数据之前就锁定了，所以我实际上需要担心这个，或者只是调试器过于简单化了？
But I am locking before I touch the shared data, so do I actually need to
worry about this, or is it just the debugger being oversimplistic?
是的警告是对的。您应该只从它们创建的线程访问Winforms控件
。 Lock在这里没有帮助。
Mattias
-
Mattias Sj？gren [C＃MVP] mattias @ mvps .org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
请回复到新闻组。
Yes the warning is right. You should only access Winforms controls
from the thread they were created on. Lock doesn''t help here.
Mattias
--
Mattias Sj?gren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
感谢您发帖。
如果您使用多线程来提高性能你的Windows窗体
应用程序，你必须小心以
线程安全的方式调用你的控件。
对Windows窗体控件的访问本质上不是线程安全的。如果你有两个或多个线程来操纵一个控件的状态，那么可能会使控件进入一个不一致的状态。其他与线程相关的错误也可能是
，包括竞争条件和死锁。确保以线程安全的方式访问您的控件非常重要
。
.NET Framework可帮助您检测何时访问您的控件以
a方式不是线程安全的。当您在
中运行应用程序时，调试器以及创建控件的线程以外的线程
尝试调用该控件，调试器会引发一个
InvalidOperationException，消息，控制控件名称从其创建的线程以外的线程访问
。
要以线程安全的方式访问控件，您应该使用
控件的Invoke方法。以下是一个示例。
delegate void WriteOutDelegate（ref string Payload）;
void test_Callback（ref string Payload）
{
object [] args = new object [1] {Payload};
this.Invoke（new WriteOutDelegate（WriteOut），args）;
}
private void WriteOut（ref string Payload）
{
this.Text = Payload;
}
希望这会对你有所帮助。
如果您有任何其他问题，或需要其他任何事情，请不要
犹豫要告诉我。
此致，
Linda Liu
Microsoft在线社区支持
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Hi,
Thank you for posting.
If you use multithreading to improve the performance your Windows Forms
applications, you must be careful to make calls to your controls in a
thread-safe way.
Access to Windows Forms controls is not inherently thread safe. If you have
two or more threads manipulating the state of a control, it is possible to
force the control into an inconsistent state. Other thread-related bugs are
possible as well, including race conditions and deadlocks. It is important
to ensure that access to your controls is done in a thread-safe way.
The .NET Framework helps you detect when you are accessing your controls in
a manner that is not thread safe. When you are running your application in
the debugger, and a thread other than the one which created a control
attempts to call that control, the debugger raises an
InvalidOperationException with the message, "Control control name accessed
from a thread other than the thread it was created on."
To make the access to your controls in a thread-safe way, you should use
the Invoke method of the control. The following is a sample.
delegate void WriteOutDelegate(ref string Payload);
void test_Callback(ref string Payload)
{
object[] args = new object[1]{Payload};
this.Invoke(new WriteOutDelegate(WriteOut),args);
}
private void WriteOut(ref string Payload)
{
this.Text = Payload;
}
Hope this will help you.
If you have any other concerns, or need anything else, please don''t
hesitate to let me know.
Sincerely,
Linda Liu
Microsoft Online Community Support
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Dave Booker写道：
Dave Booker wrote:
我有一个Thread回调Form函数改变Form数据。
当然，调试器告诉我， 跨线程操作无效：
控制''FormTest''从其创建的线程以外的线程访问。
但我锁定在我触摸共享数据之前，我是否真的需要担心这个问题，或者只是调试器过于简单？
I have a Thread making a callback to a Form function that alters Form data.
Of course, the debugger is telling me, "Cross-thread operation not valid:
Control ''FormTest'' accessed from a thread other than the thread it was
created on."
But I am locking before I touch the shared data, so do I actually need to
worry about this, or is it just the debugger being oversimplistic?
是的，你需要担心它。 UI组件具有线程亲和力 -
他们真的，除了他们自己的线程之外真的不应该被触及。
（除了调用CreateGraphics，InvokeRequired，BeginInvoke
和Invoke。）
另外一个注意事项 - 你似乎是通过
引用传递字符串引用而不使用by-ref语义。
有这个原因吗？您可能不知道参数传递的工作原理。请参阅
http://www.pobox.com/ ~sibet / csharp / parameters.html
Jon
Yes, you need to worry about it. UI components have thread affinity -
they really, really shouldn''t be touched except on their own thread.
(Aside from the calls to CreateGraphics, InvokeRequired, BeginInvoke
and Invoke.)
One further note - you appear to be passing string references by
reference without using the by-ref semantics. Is there a reason for
this? You may be unaware of how parameter passing works. See
http://www.pobox.com/~skeet/csharp/parameters.html
Jon
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