Error Two-way binding requires Path or XPath

Introduction

Worried over this exception? This happens when you haven’t set the Path= on binding. By default WPF binding will take the Path= part by default. But on controls which have a two way binding by default, this seems not to be working. You may have to set it explicitly. But in certain scenarios, you may be binding the value in a DataTemplate, for example,

 <DataTemplate x:Key="BoolValueTemplate">
    <DockPanel>
       <RadioButton IsChecked="{Binding }" GroupName="IsSelectedGroup">
       </RadioButton>
       <RadioButton IsChecked="{Binding Converter={StaticResource InvertedValueConverter}}" GroupName="IsSelectedGroup">
       </RadioButton>
    </DockPanel>
 </DataTemplate>

Here you prefer the control to take the default value which is set by the ContentControl or TemplateParent. If you try to bind it like this, you will get an exception which says like, Two-way binding requires Path or XPath. To fix this, you have to specify the path like as shown below.

Path=.
<DataTemplate x:Key="BoolValueTemplate">
    <DockPanel>
       <RadioButton IsChecked="{Binding Path=.}" GroupName="IsSelectedGroup">
       </RadioButton>
       <RadioButton IsChecked="{Binding Path=. , Converter={StaticResource InvertedValueConverter}}" GroupName="IsSelectedGroup">
       </RadioButton>
     </DockPanel>
</DataTemplate>

Now here this cannot be called as a bug, but it’s a feature which blocks developers from adding a binding which they assume to be a one way binding. Those controls which take two-way binding by default will expect developers to explicitly specify Path.

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Libish Varghese Jacob

Libish Varghese JacobI am a lead engineer at a prominent wind turbine manufacturing firm. My interests span a diverse range, and immersing myself in technology is one of them. This platform serves as my primary knowledge base, where I seek information and insights. Moreover, I utilize this platform to share my experiences and experiments, hoping they may benefit those following a similar path. It's important to note that the suggestions I express here are based on my best knowledge at the time of writing and may not necessarily represent the optimal solutions. I wholeheartedly welcome any comments you may have to improve or refine my ideas. Your feedback is greatly appreciated and valued.