DataGrid bind command to row select - wpf

Question

I want to execute a command when the user selects a row in a DataGrid.
I see it is possible to wrap cell contents in buttons (although I don't want the button style) - but I don't want to do it at the cell-level.
I also see it's possible to use behaviours to link a command to an event. But preferably I should not have to resort to behaviors for such a common task.
Is it possible to do this via plain old command databinding?
So: 1) user clicks DataGrid row 2) command on view model is fired.

Answer 1

You should use "Interactivity" assembly and SelectionChanged event.
<DataGrid AutoGenerateColumns="False" ItemsSource="{Binding People}">
<DataGrid.Columns>
<DataGridTextColumn Header="ID" Binding="{Binding ID}" />
<DataGridTextColumn Header="Name" Binding="{Binding Name}" />
</DataGrid.Columns>
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding MyCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</DataGrid>
Where "i" is namespace:
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
Also you can write binding to SelectedItem property of the DataGrid and in the set accessor you can invoke your command, but the first solution that i presented you above is better.
If you want to invoke command from main view model and pass SelectedItem from DataGrid you can use CommadParameter:
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding MyCommand}"
CommandParameter="{Binding Path=SelectedItem, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGrid}}" />
</i:EventTrigger>
</i:Interaction.Triggers>
When items has own command you can use following code:
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding Path=SelectedItem.MyCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGrid}}" />
</i:EventTrigger>
</i:Interaction.Triggers>
Or if elements has own view model that is assigned to it's DataContext, you can use following code:
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding Path=SelectedItem.DataContext.MyCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGrid}}" />
</i:EventTrigger>
</i:Interaction.Triggers>

Answer 2

Be advised that #kmatyaszek's answer is outdated in .NET 5.0 and above, we should use Microsoft.Xaml.Behaviors instead of Microsoft.Expression.Interactions.
So the i in the namespace should be:
xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
See here for details.