wpf combo box default value

Question

I'm trying to default the Combo Box selected item to index = 0 when the SelectedValue is Null. What is wrong with the data trigger ? Error: SelectedIndex is not recognized property

 <ComboBox x:Name="ACombobox" ItemsSource="{Binding Mode=OneWay, Source={StaticResource AList}}" DisplayMemberPath="TypeName" SelectedValuePath="TypeName" SelectedValue="{Binding AnObj.Type, Mode=TwoWay}" > <ComboBox.Triggers> <DataTrigger Binding="{Binding}" Value="{x:Null}"> <Setter Property="SelectedIndex" Value="0" /> </DataTrigger> </ComboBox.Triggers> </ComboBox>

Abin · Accepted Answer · 2016-07-14 19:47:25Z

You should do it by creating a style trigger like below

<ComboBox x:Name="ACombobox" ItemsSource="{Binding Mode=OneWay, Source={StaticResource AList}}" DisplayMemberPath="TypeName" SelectedValuePath="TypeName" SelectedValue="{Binding AnObj.Type, Mode=TwoWay}" > <Style TargetType="ComboBox"> <Style.Triggers> <DataTrigger Binding="{Binding}" Value="{x:Null}"> <Setter Property="SelectedIndex" Value="0" /> </DataTrigger> </Style.Triggers> </Style> </ComboBox>

The error says that it does not have a qualifying type name so by creating a style it apply to Combobox when you set the TargetType="ComboBox"

<ComboBox x:Name="ACombobox" ItemsSource="{Binding AList}" DisplayMemberPath="TypeName" SelectedValuePath="TypeName" SelectedValue="{Binding AnObj.Type, Mode=TwoWay}" > <ComboBox.Resources> <Style TargetType="ComboBox"> <Style.Triggers> <DataTrigger Binding="{Binding SelectedItem}" Value="{x:Null}"> <Setter Property="SelectedIndex" Value="0" /> </DataTrigger> </Style.Triggers> </Style> </ComboBox.Resources> </ComboBox>

This works for me.

Example with StaticResource

 <Window.Resources> <x:Array x:Key="StringList" Type="System:String"> <System:String>Line 1</System:String> <System:String>Line 2</System:String> <System:String>Line 3</System:String> <System:String>Line 4</System:String> </x:Array> </Window.Resources> <ComboBox ItemsSource="{StaticResource StringList}" > <ComboBox.Resources> <Style TargetType="ComboBox"> <Style.Triggers> <Trigger Property="SelectedItem" Value="{x:Null}"> <Setter Property="SelectedIndex" Value="0"/> </Trigger> </Style.Triggers> </Style> </ComboBox.Resources> </ComboBox>

Abin: I got an exception : Items Collection must be empty before using Items Source.
Alist is a static resource defined in xaml. If I take this style out everything works fine and I get no errors.
Put your Style in ComboBox.Resources @AbinMathew . Either way I still can't get SelectedIndex working except on startup
@AbinMathew this does not work: gist.github.com/anonymous/df5a2b9f3f393543367ddf5c02d2f6ff

Collectives™ on Stack Overflow

wpf combo box default value

1 Answer 1

12 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

12 Comments

Related