Problem with SelectedItem of WPF Editable ComboBox with DataTemplate

问题

I’m having the following issue with WPF ComboBox:

XAML:

<Window.Resources>
  <ResourceDictionary>
    <DataTemplate DataType="{x:Type this:Data}">

      <ComboBox IsTextSearchEnabled="False" IsEditable="True" 
                Text="{Binding Value}" ItemsSource="{Binding Menu}"/>

    </DataTemplate>
  </ResourceDictionary>
</Window.Resources>

<StackPanel>
  <ContentControl Content="{Binding}"/>
  <Button Click="ChangeData_Click">Change Data</Button>
</StackPanel>

Code behind:

public Window1()
{
    InitializeComponent();
    DataContext = new Data();
}

void ChangeData_Click(object sender, RoutedEventArgs e)
{
    DataContext = new Data();
}

I open the window and get ComboBox, bounded to my data model, I select some item (e.g. 1), all is dandy.

I change the data context to a new data model – the selected item is (to my surprise) 1... Where I don't expect any selected item...

I suspect it has something to do with the combo box which search disabled and editable, but I’m not sure what was the problem.

I found a work around: call UpdateLayout() on the ContentControl bounded to the DataContext, but it’s ugly.

Is that WPF bug? Is it all my fault?

Please Help

回答1:

I've submitted the same question to MSDN WPF Forum and it seems like a Microsoft bug. There's a workaround I found, ugly, but it's working. Here's the modified code behind:

    public Window1()
    {
        InitializeComponent();
        DataContext = new Data();
        DataContextChanged += delegate { contentControl.UpdateLayout(); };
    }

    void ChangeData_Click(object sender, RoutedEventArgs e)
    {
        DataContext = null;
        DataContext = new Data();
    }

Note that both setting the DataContext to null and calling UpdateLayout() on DataContextChanged are needed to solve this issue.

来源：https://stackoverflow.com/questions/1389040/problem-with-selecteditem-of-wpf-editable-combobox-with-datatemplate