Issue with doubleclick on datagrid

Question

I have the following on a datagrid in my C# code:

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

It works for the most part except if user first selects the row (single click) and then tries double-clicking the row. In this situation the CmdTransUnitFillerRowDblClick code is never fired for processing.

So, how can I get the CmdTransUnitFillerRowDblClick to fire correctly on a double-click when the row is already selected?
Since someone may ask:

private void ExecutecmdTransUnitFillerRowDblClick(object parameter)  
{
    if (DgTransUnitFillerSelectedItem != null)
        TransUnitFillerDoubleClick(DgTransUnitFillerSelectedItem.CollectionRowId);
}

Answer 1

On top of your existing InputBinding, you can use a Style to attach the InputBinding to each cell:

<Style TargetType="DataGridCell">
    <Setter Property="local:MouseCommands.LeftDoubleClick" Value="ApplicationCommands.New" />
</Style>

This requires use of the MouseCommands class from here.

public static class MouseCommands
{
    private static void LeftDoubleClickChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
    {
        var control = (Control)sender;

        if (args.NewValue != null && args.NewValue is ICommand)
        {
            var newBinding = new MouseBinding(args.NewValue as ICommand, new MouseGesture(MouseAction.LeftDoubleClick));
            control.InputBindings.Add(newBinding);
        }
        else
        {
            var oldBinding = control.InputBindings.Cast<InputBinding>().First(b => b.Command.Equals(args.OldValue));
            control.InputBindings.Remove(oldBinding);
        }
    }

    public static readonly DependencyProperty LeftDoubleClickProperty =
        DependencyProperty.RegisterAttached("LeftDoubleClick",
            typeof(ICommand),
            typeof(MouseCommands),
            new UIPropertyMetadata(LeftDoubleClickChanged));

    public static void SetLeftDoubleClick(DependencyObject obj, ICommand value)
    {
        obj.SetValue(LeftDoubleClickProperty, value);
    }

    public static ICommand GetLeftDoubleClick(DependencyObject obj)
    {
        return (ICommand)obj.GetValue(LeftDoubleClickProperty);
    }
}

Though I think a cleaner way is to just handle the MouseDoubleClick event in the code-behind and manually raise the Command execution by calling your ViewModel directly, or calling .Execute() on the command.

Answer 2

See my answer to another related question. The problem is that the datagrid no longer has the focus after the user selects a row (or cell, actually); the cell that the user clicked in the datagrid does. So you have to change the focus back to the datagrid to allow this.

Change:

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

To:

<DataGrid.InputBindings>  
    <MouseBinding Gesture="LeftDoubleClick" Command="{Binding CmdTransUnitFillerRowDblClick}" />  
    <MouseBinding Gesture="LeftClick" Command="{Binding CmdTransUnitFillerRowClick}" />  
</DataGrid.InputBindings>

...and add:

private void ExecutecmdTransUnitFillerRowClick(object parameter)  
{
    if (DgTransUnitFillerSelectedItem != null)
        The_Name_Of_Your_DataGrid.Focus();
}