从后台线程更新UI

Question

This is just a curious question. Which one is the best way to update UI from another thread. First, this one:

private delegate void MyDelegateMethod();
void MyMethod()
{
    if (unknowncontrol.InvokeRequired)
    {
        this.BeginInvoke(new MyDelegateMethod(MyMethod));
        return;
    }
    unknowncontrol.property = "updating!";
}

On the other hand:

Invoke((System.Threading.ThreadStart)delegate()
{
    unknowncontrol.property = "updating!";
});

Or, is there a better way to do this?

Of course this is for WinForms, for WPF there's the dispatcher. How is the code for WPF?

I'm asking, 'cause, in the past I experienced errors when updating UI from a raised event using both of the options above. The kind of error like: "there is no source code available". I assume all of us have seen them :D.

Thanks, and have a nice day!

Answer 1

Check out Roy Osherove's blog post on this: http://osherove.com/blog/2006/3/1/the-3-ways-to-create-a-thread-safe-gui-with-net-20-with-one.html

delegate void Func<T>(T t);
Func del = delegate
{

  // UI Code goes here
};
Invoke(del);

Answer 2

The default Action delegate worked 90% of the time:

private void Log(String value)
{
    // Verify that we're on the same thread
    if (textBox1.InvokeRequired)
    {
        // We're not on the same thread - Invoke the UI thread
        textBox1.Invoke(new Action<string>(Log), value);
        return;
    }

    // We're on the same thread - Update UI
    textBox1.Text += value + "\r\n";
}

private void OnSomethingHappened()
{
    Log("Something happened!");
}

Answer 3

Use [Dispatcher.Invoke(DispatcherPriority, Delegate)] to change the UI from another thread or from background.

Step 1 . Use the following namespaces

using System.Windows;
using System.Threading;
using System.Windows.Threading;

Step 2 . Put the following line where you need to update UI

Application.Current.Dispatcher.Invoke(DispatcherPriority.Background, new ThreadStart(delegate
{
    //Update UI here
}));

Syntax

 [BrowsableAttribute(false)] public object Invoke( DispatcherPriority priority, Delegate method ) 

Parameters

priority

Type: System.Windows.Threading.DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, the specified method is invoked.

method

Type: System.Delegate

A delegate to a method that takes no arguments, which is pushed onto the Dispatcher event queue.

Return Value

Type: System.Object

The return value from the delegate being invoked or null if the delegate has no return value.

Version Information

Available since .NET Framework 3.0

Answer 4

I typically used the first model, but that's only because I found it clearer. There isn't really going to be an effective difference between the two.

Answer 5

如我所见，最好的方法是设置ui元素的属性绑定到的CLR属性。

Answer 6

The first method (BeginInvoke) ensures that the UI update code executes on the same thread that created the control. The 2nd method does not. Having all UI updating code execute on the same thread avoids alot of threading issues and allows you to use controls that are not necessarily thread-safe.