How to bind Click in combobox in the view model? - wpf

Question

I would like to do something when a click in a combobox, in a MVVM pattern.
I am trying to use input bindings in this way:
<ComboBox.InputBindings>
<KeyBinding Key="Return" Command="{Binding BuscarKeyDownCommand}"/>
<MouseBinding Gesture="LeftClick" Command="{Binding TiposFacturasMouseLeftClickCommand}"/>
</ComboBox.InputBindings>
In my view model I have this code:
private RelayCommand _tiposFacturasMouseLeftClickCommand;
public RelayCommand TiposFacturasMouseLeftClickCommand
{
get { return _tiposFacturasMouseLeftClickCommand ?? (_tiposFacturasMouseLeftClickCommand = new RelayCommand(param => TiposFacturasMouseLeftClick(), param => true)); }
}
private async void TiposFacturasMouseLeftClick()
{
try
{
//search for items.
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}
But the command is not fired.
However, the key return input binding works as expected.
Which is the best way to bind the click event of the combobox? Or perhaps there are another better solution to search the items on the combobox the first time that I click on it.
Thanks.

Answer 1

You could install the Microsoft.Xaml.Behaviors.Wpf NuGet package and use an EventTrigger to invoke a command when an event is raised, e.g.:
<ComboBox xmlns:i="http://schemas.microsoft.com/xaml/behaviors">
<i:Interaction.Triggers>
<i:EventTrigger EventName="PreviewMouseLeftButtonDown" >
<i:InvokeCommandAction Command="{Binding TiposFacturasMouseLeftClickCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
<ComboBoxItem>1</ComboBoxItem>
<ComboBoxItem>2</ComboBoxItem>
<ComboBoxItem>3</ComboBoxItem>
</ComboBox>
Please refer to this blog for more informatio about how to handle events in MVVM.