检测是否在WPF和Winforms中的UI线程上

Question

我在下面编写了一个断言方法Ensure.CurrentlyOnUiThread(),用于检查当前线程是否为UI线程.

• 这在检测Winforms UI线程时是否可靠？
• 我们的应用程序是混合WPF和Winforms,如何最好地检测有效的WPF UI线程？
• 有一个更好的方法吗？也许代码合同？

Ensure.cs

using System.Diagnostics;
using System.Windows.Forms;

public static class Ensure
{
    [Conditional("DEBUG")]
    public static void CurrentlyOnUiThread()
    {
        if (!Application.MessageLoop)
        {
            throw new ThreadStateException("Assertion failed: not on the UI thread");
        }
    }
}

Answer 1

不要用

if(Dispatcher.CurrentDispatcher.Thread == Thread.CurrentThread)
{
   // Do something
}

Dispatcher.CurrentDispatcher将,如果当前线程没有调度程序,则创建并返回Dispatcher与当前线程关联的新线程.

相反,这样做

Dispatcher dispatcher = Dispatcher.FromThread(Thread.CurrentThread);
if (dispatcher != null)
{
   // We know the thread have a dispatcher that we can use.
}

为了确保您拥有正确的调度程序或在正确的线程上,您有以下选项

Dispatcher _myDispatcher;

public void UnknownThreadCalling()
{
    if (_myDispatcher.CheckAccess())
    {
        // Calling thread is associated with the Dispatcher
    }

    try
    {
        _myDispatcher.VerifyAccess();

        // Calling thread is associated with the Dispatcher
    }
    catch (InvalidOperationException)
    {
        // Thread can't use dispatcher
    }
}

CheckAccess()并且VerifyAccess()不会出现在intellisense中.

此外,如果你不得不诉诸这些东西,可能是由于糟糕的设计.您应该知道哪些线程运行程序中的代码.

Answer 2

在WinForms中你通常会使用

if(control.InvokeRequired) 
{
 // Do non UI thread stuff
}

对于WPF

if (!control.Dispatcher.CheckAccess())
{
  // Do non UI Thread stuff
}

我可能会写一个使用Generic约束的方法来确定你应该调用哪些.例如

public static bool CurrentlyOnUiThread<T>(T control)
{ 
   if(T is System.Windows.Forms.Control)
   {
      System.Windows.Forms.Control c = control as System.Windows.Forms.Control;
      return !c.InvokeRequired;
   }
   else if(T is System.Windows.Controls.Control)
   {
      System.Windows.Controls.Control c = control as System.Windows.Control.Control;
      return c.Dispatcher.CheckAccess()
   }
}

Answer 3

对于WPF:

// You are on WPF UI thread!
if (Thread.CurrentThread == System.Windows.Threading.Dispatcher.CurrentDispatcher.Thread)

对于WinForms:

// You are NOT on WinForms UI thread for this control!
if (someControlOrWindow.InvokeRequired)

Answer 4

对于WPF,我使用以下内容:

public static void InvokeIfNecessary (Action action)
{
    if (Thread.CurrentThread == Application.Current.Dispatcher.Thread)
        action ();
    else {
        Application.Current.Dispatcher.Invoke(action);
    }
}

关键是检查Dispatcher.CurrentDispatcher(它将为您提供当前线程的调度程序),您需要检查当前线程是否与应用程序的调度程序或其他控件匹配.

Answer 5

也许Control.InvokeRequired(WinForms)和Dispatcher.CheckAccess(WPF)对你好吗？