WPF TabControl选项卡更改未刷新

Question

I have a WPF TabControl with two TabItems . I am trying to change the selected tab on code behind on a Button click event and execute some other code. In this example:

private void Button_Click(object sender, RoutedEventArgs e)
{
    ConvertDataTabControl.SelectedIndex = 1;
    System.Threading.Thread.Sleep(2000);
    ...
}

I would expect the UI to refresh and move from Tab 0 to Tab 1 and only then execute the Sleep method, but the UI is refreshed only after Button_Click finishes execution. I tried calling InvalidateVisual , but it does not work.

Is there a way to force the UI to refresh before executing Sleep ?

Answer 1

Your code runs on the UI thread by default, so nothing else can be executed on the UI thread (such as updating the layout) until the thread finishes executing.

There are many ways of releasing control of the UI thread before the code finishes executing, but I find the simplest is to use a Task from the Task Parallel Library which can be used to run code on a separate thread.

For example,

Task.Factory.StartNew(() =>
{
    Thread.Sleep(2000);

    // Other code here
});

It should be noted that UI objects can only be modified on the UI thread, so if your "other code here" updates a UI object, you'll probably want to use the Dispatcher to execute code on the UI thread, like this:

Dispatcher.BeginInvoke(() =>
{
    // Code to update the UI
});

Answer 2

try

Dispatcher.BeginInvoke(()=>
{
    ConvertDataTabControl.SelectedIndex = 1;
});

Answer 3

The problem is you are doing your work (sleep) on the UI thread. You can use a task/backgroundworker/etc to do the work in an other thread and then do set the ui changes back to the UI thread:

private void Button_Click(object sender, RoutedEventArgs e)
{
    Dispatcher callback = Dispatcher.CurrentDispatcher;
    ThreadPool.QueueUserWorkItem(new WaitCallback((o) =>
    {
         //Do some work
         System.Threading.Thread.Sleep(2000);

         //callbackk to ui thread to do ui work. You can also use BeginInvoke...
         callback.Invoke(new Action(() => {ConvertDataTabControl.SelectedIndex = 1;}));

         //Do some more work
         System.Threading.Thread.Sleep(2000);
         ...
    }
}

It is just a example to get the idea.