Why MouseDoubleClick-EventTrigger for DataGrid works only once on each row!?

Question

Hi,
The XAML code is as below.

<DataGrid x:Name="LabelPrintOutputDataList" SelectionMode="Single" ItemsSource="{Binding Path=LabelPrintOutDatas}" AutoGenerateColumns="False" IsReadOnly="True" Visibility="{Binding Path=IsGridVisible,Converter={StaticResource boolToVisibility}}" CanUserSortColumns="False" CanUserAddRows="False" CanUserDeleteRows="False" CanUserReorderColumns="False" CanUserResizeColumns="False" SelectionUnit="FullRow" >
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="MouseDoubleClick">
                    <i:InvokeCommandAction Command="{Binding DoubleClickCommand}"  CommandParameter="{Binding ElementName=LabelPrintOutputDataList, Path=CurrentItem}"/>
                </i:EventTrigger>
                <i:EventTrigger EventName="SelectionChanged">
                    <i:InvokeCommandAction Command="{Binding SelectedItemChangedEvent}"  CommandParameter="{Binding ElementName=LabelPrintOutputDataList, Path=CurrentItem}"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
            <DataGrid.Columns>
....

 </DataGrid.Columns>
        </DataGrid>

=================================== ViewModel below

public class LabelPrintOutputMainViewModel : BindableBase
{
public LabelPrintOutputMainViewModel(..........){
DoubleClickCommand = new DelegateCommand<LabelPrintOutData>(LabelPrintOutputListDoubleClicked);
}

private void LabelPrintOutputListDoubleClicked(LabelPrintOutData labelprintoutData)
{
if (labelprintoutData == null) return;
if (labelprintoutData.TRACE == null) return;
this.MakeNewPrintWindow();
this.eventAggregator.GetEvent<LabelPrintOutDoubleClickEvent>().Publish(labelprintoutData);
productlabelprintoutView.ShowDialog();
labelprintoutData = null;
}

public DelegateCommand<LabelPrintOutData> DoubleClickCommand { get; private set; }

}

The values of parameter in LabelPrintOutputListDoubleClicked ( ie; labelprintoutData) method is null while we click more than once. productlabelprintoutView.ShowDialog(); will execute only once for each row in the grid. What would be the reason?

Answer 1

Hi,

Welcome to our Microsoft Q&A platform!

We can continue to discuss this Thread.

why-mousedoubleclickeventtrigger-for-datagrid-works-only-once-on-each-row

I think there is something wrong with the parameters of your LabelPrintOutputListDoubleClicked method,you can see my Test method .

 public class MyViewMode  
    {  
        public ICommand DoubleClickCommand { get; set; }  
        public MyViewMode()  
        {  
              
            DoubleClickCommand = new MyDelegateCommand();  
            (DoubleClickCommand as MyDelegateCommand).ExecuteCommand = Test;  
            (DoubleClickCommand as MyDelegateCommand).CanExecuteCommand = CanTest;  
        }  
  
        private void Test(object para)  
           
        {  
            MessageBox.Show(GetCellValue((DataGridCellInfo)para).ToString());  
        }  
        public object GetCellValue(DataGridCellInfo cellInfo)  
  
        {  
            if (cellInfo != null)  
            {  
                var column = cellInfo.Column as DataGridBoundColumn;  
                if (column != null)  
                {  
                    var element = new FrameworkElement() { DataContext = cellInfo.Item };  
                    BindingOperations.SetBinding(element, FrameworkElement.TagProperty, column.Binding);  
                    var cellValue = element.Tag;  
  
                    if (cellValue != null)  
  
                        return (cellValue);  
  
                }  
            }  
            return (null);  
        }  
  
        private bool CanTest(object para)  
        {  
            return true;  
        }  
    }  

MVVM Code:

 <Grid>  
        <DataGrid Name="LabelPrintOutputDataList">  
            <i:Interaction.Triggers>  
                <i:EventTrigger EventName="MouseDoubleClick">  
                    <i:InvokeCommandAction Command="{Binding DoubleClickCommand}"  CommandParameter="{Binding ElementName=LabelPrintOutputDataList, Path=CurrentCell}"/>  
                </i:EventTrigger>  
            </i:Interaction.Triggers>  
        </DataGrid>  
    </Grid>  

Thanks.

Answer 2

Hello Alex,

would you please disclose your MyDelgateCommand or do you have the complete example somewhere??

Thanks a beginner..