WPF ComboBox: How to you utilise a generic ItemContainerStyle with binding

Question

I want to utilise a generic style for my ComboBoxItem content and have the text content bound to different properties on my underlying class. So this is the best I can come up with but the bindings are hard coded. So for every class bound to a combobox using this ItemContainerStyle I'd have to implement a "MainText" and "SubText" property.

Question is, is there a way to have the binding soft coded so where the style referenced from a combobox I can specify which string properties of the underlying class are used.

<Style TargetType="{x:Type ComboBoxItem}"  x:Key="ComboBoxItemStyleA1">
        <Setter Property="Template" >
            <Setter.Value>
                <ControlTemplate TargetType="ComboBoxItem">

                    <Border x:Name="BB" Padding="8,3,8,3" Background="DarkGreen">
                        <StackPanel Margin="0">
                            <TextBlock Foreground="White"   FontSize="16" Text="{Binding MainText}"/>
                            <TextBlock Foreground="White"   FontSize="8" Text="{Binding SubText}"/>
                        </StackPanel>
                    </Border>
                        <ControlTemplate.Triggers>

                        <Trigger Property="IsSelected" Value="True">
                            <Setter Property="Background" TargetName="BB" Value="#FF256294"/>
                            <Setter Property="Foreground" Value="White"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

And to use the style...

<ComboBox ItemsSource="{Binding Items}" 
    ItemContainerStyle="{StaticResource ComboBoxItemStyleA1}" />

Further to dowhilefor's answer (many many thanks - WPF is great but sure is a voyage of discovery)

I used a data template to define the cell look originally - and then wanted to use a comboboxitem based style with a control template defined where I could specify the onmouseover triggers. i.e. these were to change the background color etc.

Butj a) I couldn't remove the Border section of the template above - the triggers are tied to it by targettype="BB". so I kind of wanted to get the trigger bound to the container such that the datatemplate would pick up the background from the template binding but not sure how to get this plumbed in.

b) I realised that even if I comment out the BB specific bindings on the triggers just to get it to run - the combobox doesn't find and use the DataTemplate I defined. Seems that defining the controltemplate in my comboboxitemstyle stops it picking up the datatemplate.

I hope I make sense here - bottom line is I just want a style that I can apply with triggers in that set the background color of my cobobox item. It should not know what the data is - i.e. be able to plug in a datatemplate that will (template ?) bind to this background color.

Many thanks for the very fast response.

btw I'm using ItemContainerStyle in conjuction with ItemTemplate so I can have a different representation in the dropdown to what appears in the combobox list

dowhilefor dowhilefor · Accepted Answer · 2012-12-08T02:18:17

First of all don't use the ItemContainerStyle for that. To be more precise never have any Bindings to the datacontext inside an ItemContainerStyle, at least try not. Why? The Style is used for defining the appearance of a combobox item disregarding the content. If you want to define how the content should look like, you use a DataTemplate for that. There are multiple ways to tell the combobox where he can find a proper DataTemplate for the Data you supply. Checkout the property ItemTemplate, ItemTemplateSelector and search for implicit styles, to find out more about them.

So to your problem, create one ItemContainerStyle for you combobox (if you really have to anymore) which doesn't care about the object that will be put into. Now you still need to provide multiple DataTemplates each and everyone with the knowledge of the data object that you want to be templated. There is no way around it, there is no soft databinding. Just try to keep your templates small and simple. If for some reason you need the exact same template, but your properties are just named differently, why not use a wrapper item for the DataContext with the properties Caption, Description and you can decide in code how these properties are filled with your real data wrapped into this object.

WPF ComboBox: How to you utilise a generic ItemContainerStyle with binding

1 Answers