I have a ComboBox with a custom ItemsTemplateSelector. The Items for the control are defined in xaml, like so:
<ComboBox ItemTemplateSelector="{StaticResource CommonListSelectorTemplates}" >
<local:MyItem Heading="First" Text="First Item"/>
<local:MyItem Heading="Second" Text="Second Item"/>
<local:MyItemWithValue Heading="Third" Text="Third Item" Value="{Binding TheValue}" />
</ComboBox>
The third item has a Value property that I wish to bind to the TheValue property on the ComboBox's DataContext. This binding fails with the following error:
"Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=TheValue; DataItem=null; target element is 'MyItemWithValue' (HashCode=49465727); target property is 'Value' (type 'Int32')"
I guess it's becuase the Items collection does not use the ComboBox's DataContext. I have tried different permutations of RelativeSource without success, so my question is: What is the best way to accomplish the binding?
EDIT:
RV1987 answered my question as it was stated. However, what I want is for the binding to be two-way, and neither of the solutions proposed seem to work for this. The trouble may be that I can't get the binding in the proxy to be two-way; the compiler refuses to accept
DataContext="{Binding, Mode=TwoWay}"
ComboboxItems are not part of visual tree so they are not connected to the data context of the Combobox. You have to use the proxy binding to refer to the dataContext. For detailed and clean approach please have a look at this link -
Also, look at this (same issue but in this case its datagrid in place of combobox) as suggested by AngelWPF, this was also something new to me -
Bind datagrid column visibility MVVM
Edit- Moreover, you need to set binding mode Two way in your comboboxitem instead of setting it in StaticResource. This should work -
<local:MyItemWithValue Heading="Third" Text="Third Item" Value="{Binding TheValue, Mode=TwoWay}" />