How to Bind WPF ListBox SelectionChanged Events to ViewModel Commands?

Bind UI events to commands in WPF ViewModel

Following the MVVM architecture, moving UI events to ViewModel is more conducive to code maintenance and expansion. This article will focus on how to transfer the ListBox's SelectionChanged event from the code-behind file to the ViewModel, and use the provided code snippet as an example.

Solution

To do this, we need to use EventTrigger together with InvokeCommandAction (in the System.Windows.Interactivity namespace):

<code class="language-xml"><ListBox ...>
  <i:Interaction.Triggers>
    <i:EventTrigger EventName="SelectionChanged">
      <i:InvokeCommandAction Command="{Binding SelectedItemChangedCommand}" />
    </i:EventTrigger>
  </i:Interaction.Triggers>
</ListBox></code>

Reference System.Windows.Interactivity

• Add a reference to the assembly via Add Reference > Assembly > Extensions.
• Use full namespace: xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity".

Additional Notes

The
• Command property is bound to the command defined in the ViewModel.
• This pattern simplifies UI event handling and enhances separation of concerns.
• Be sure to reference the System.Windows.Interactivity namespace as directed to ensure successful implementation.

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