WPF DataGrid: CommandBinding to a double click instead of using Events

Another solution is to add input bindings, and to bind the selectedItem to a property so you'll know which one was selected:

<DataGrid SelectedItem="{Binding SelectedItem}">
      <DataGrid.InputBindings>
          <MouseBinding Gesture="LeftDoubleClick" Command="{Binding SomeCommand}"/>
     </DataGrid.InputBindings>
</DataGrid>

No need for attached behaviors or custom DataGrid subclasses here.

In your DataGrid, bind ItemsSource to an ICollectionView. The trick here is to set IsSynchronizedWithCurrentItem="True" which means the selected row will be the current item.

The second part of the trick is to bind CommandParameter to the current item with the forward slash syntax.

When a row is double clicked, the command will be executed with the clicked row as argument.

<DataGrid
    ItemsSource="{Binding CollectionView}"
    IsSynchronizedWithCurrentItem="True">
    <DataGrid.InputBindings>
        <MouseBinding
            MouseAction="LeftDoubleClick"
            Command="{Binding DoubleClickCommand}"
            CommandParameter="{Binding CollectionView/}"/>
    </DataGrid.InputBindings>
</DataGrid>

This is how a (simplified) version of the view model would look:

class MyViewModel
{
    public ICollectionView CollectionView { get; set; }

    public ICommand DoubleClickCommand { get; set; }
}

Use this library

Sample binding to datagrid event:

<DataGrid xmlns:command="clr-namespace:AttachedCommandBehavior;assembly=AttachedCommandBehavior"
    command:CommandBehavior.Event="MouseDoubleClick"
    command:CommandBehavior.Command="{Binding TestCommand}" />

But this code is better, because raises on row clicks only:

<DataGrid>
    <DataGrid.Resources>
        <Style TargetType="DataGridRow">
            <Setter Property="command:CommandBehavior.Event" Value="MouseDoubleClick"/>
            <Setter Property="command:CommandBehavior.Command" Value="{Binding DataContext.TestCommand, RelativeSource={RelativeSource FindAncestor, AncestorType=DataGrid}}"/>
        </Style>
    </DataGrid.Resources>
</DataGrid>

Or, you could create a derived class

public class CustomDataGrid : DataGrid
{
    public ICommand DoubleClickCommand
    {
        get { return (ICommand)GetValue(DoubleClickCommandProperty); }
        set { SetValue(DoubleClickCommandProperty, value); }
    }

    // Using a DependencyProperty as the backing store for DoubleClickCommand.  This    enables animation, styling, binding, etc...
    public static readonly DependencyProperty DoubleClickCommandProperty =
        DependencyProperty.Register("DoubleClickCommand", typeof(ICommand), typeof(CustomDataGrid), new UIPropertyMetadata());

    public CustomDataGrid()
        : base()
    {            
        this.PreviewMouseDoubleClick += new MouseButtonEventHandler(CustomDataGrid_PreviewMouseDoubleClick);
    }


    void CustomDataGrid_PreviewMouseDoubleClick(object sender, MouseButtonEventArgs e)
    {
        if (DoubleClickCommand != null)
        {
            DoubleClickCommand.Execute(null);
        }
    }


}

and in XAML simply bind to the newly created command

<CustomDataGrid DoubleClickCommand="{Binding DoubleClickCommand}">