WPF Combobox binding

Question

I got two Comboboxes and both of them have binding with the same Source.

<ComboBox ItemsSource="{Binding Source={StaticResource UsersViewSource}}"

And when I change something in the first one, it reflects also to the second one. And I dunno how to keep their SelectedItem values separately, using the same ItemsSource.

score 11 · Accepted Answer · answered Mar 16 '10 at 23:17

The IsSynchronizedWithCurrentItem property should be set to False:

true if the SelectedItem is always synchronized with the current item in the ItemCollection; false if the SelectedItem is never synchronized with the current item; null if the SelectedItem is synchronized with the current item only if the Selector uses a CollectionView. The default value is null.

Here's a sample:

<Page
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
 xmlns:sys="clr-namespace:System;assembly=mscorlib"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
   <Page.Resources>
      <x:Array x:Key="myStrings" Type="sys:String">
         <sys:String>one</sys:String>
         <sys:String>two</sys:String>
         <sys:String>three</sys:String>
         <sys:String>four</sys:String>
         <sys:String>five</sys:String>
      </x:Array>
   </Page.Resources>

<StackPanel Width="200">
    <ComboBox IsSynchronizedWithCurrentItem="False" Margin="25"
    ItemsSource="{Binding Source={StaticResource myStrings}}" />

    <ComboBox IsSynchronizedWithCurrentItem="False"  Margin="25"
    ItemsSource="{Binding Source={StaticResource myStrings}}" />
</StackPanel>

</Page>

The irony of your answer is that - as your quote explains - the `IsSynchronizedWithCurrentItem="False"` in your quoted code is completely unnecessary, because you're not binding to a `CollectionView`. If you take those attributes out, the comboboxes still aren't linked. — Dan Puzey, Mar 16 '10 at 23:23
Agreed that it may not be the best example, but set the value to True and they do synchronize as if they were bound to a CollectionView (my assumption). If indeed this does not work with a CollectionView, then be all means I shall delete the answer and walk away learning something myself. — Metro Smurf, Mar 17 '10 at 00:01
Threw together a quick project and tested to see if the IsSynchronizedWithCurrentItem property will work with a CollectionView and it does indeed work. Admittedly my answer isn't exactly correct, but it does provide a quick Kaxaml example ;) — Metro Smurf, Mar 17 '10 at 01:36

score 2 · Answer 2 · answered Mar 16 '10 at 22:58

2

You just need to set the IsSynchronizedWithCurrentItem property to false (by default it's null)

answered Mar 16 '10 at 22:58

Thomas Levesque

286,951
70
623
758

score 1 · Answer 3 · answered Mar 16 '10 at 23:20

I'd guess (from the name of your binding) that the reason this is happening is that you're binding to a CollectionViewSource (that wraps a collection). This class is a proxy that WPF uses that includes (amongst other things) the selected item of a collection. Obviously if you're sharing this collection between two comboboxes, you're also sharing the selected item.

If you set ItemsSource to something that's not a CollectionViewSource, the control will automatically wrap it in one. So, my suggestion would be to bind directly to a collection instead of wrapping in a CollectionViewSource - or, alternatively, create two CollectionViewSource instances, one for each ComboBox.

score 0 · Answer 4 · answered Mar 16 '10 at 22:39

0

You can separately bind the SelectedItem property for each combo box separately.

i.e.

SelectedItem={Binding SelectedItem1}

This way when each one's item gets set, it gets stored into a different place.

answered Mar 16 '10 at 22:39

Chris

26,744
48
193
345

WPF Combobox binding

4 Answers4

Linked