CODEWITHSUNDEEP
c#wpfxaml
Ranish
Ranish

Reputation: 927

Button inside the Datagrid not getting Fired due to PreviewMouseLeftButtonDown

I am working on a WPF application.

As per requirement I want to show list of item in data grid. Each row also having a “DELETE” button, using this button we can deleted the corresponding item. I also want Drag and Drop feature for the Grid. That is user can move the rows up/down.

I am using “PreviewMouseLeftButtonDown” and “Drop” event of the datagrid to implement the Drag and Drop feature.

For DELETE button , I have bind the Delete Command.

Command="{Binding ElementName=viewName,Path=DataContext.DeleteCommand}"

I also tried 

 Command="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGrid}}, Path=DataContext.DeleteCommand}"

Now the issue is , when I click the “DELETE” button, the delete command handler not getting fired. But if I remove the “PreviewMouseLeftButtonDown” and “Drop” events of the data grid , the delete command handler working perfectly.

Also I noticed that ,Even if commented all code inside the “PreviewMouseLeftButtonDown” after add the PreviewMouseLeftButtonDown event, it also block the execution of Delete command handler. 

                    <DataGridTemplateColumn Width="35"  >
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <Button Width="30" Content="X"     Command="{Binding ElementName=viewCSW,Path=DataContext.DeleteCommand}"    HorizontalAlignment="Center" Margin="0,0,0,0" />
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>

                </DataGrid.Columns>
                <DataGrid.RowStyle>
                    <Style TargetType="DataGridRow">
                        <Setter Property="Height" Value="25"/>
                    </Style>
                </DataGrid.RowStyle>

Code of PreviewMousedown

  private void dgEmployee_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {

            prevRowIndex = GetDataGridItemCurrentRowIndex(e.GetPosition);

            if (prevRowIndex < 0)
                return;
            dgEmployee.SelectedIndex = prevRowIndex;

            var selectedEmployee = dgEmployee.Items[prevRowIndex];//as Employee;

            if (selectedEmployee == null)
                return;
            //Now Create a Drag Rectangle with Mouse Drag-Effect
            //Here you can select the Effect as per your choice
            DragDropEffects dragdropeffects = DragDropEffects.Move;

            if (DragDrop.DoDragDrop(dgEmployee, selectedEmployee, dragdropeffects)
                                != DragDropEffects.None)
            {
                //Now This Item will be dropped at new location and so the new Selected Item
                dgEmployee.SelectedItem = selectedEmployee;
            }


            //      sourceElement.CaptureMouse();
            //  return;

        }

I am struggling with this issue.

If any one have a solution, Please let me know.

Thanks, Ranish

Upvotes: 3

Views: 1257

Answers (1)

Jason Fry
Jason Fry

Reputation: 1234

Move the DragDrop.DoDragDrop call to the datagrid's MouseMove event:

private void dgEmployee_MouseMove(object sender, MouseEventArgs e)
    {
        if(e.LeftButton == MouseButtonState.Pressed)
        {
            Employee selectedEmp = dgEmployee.Items[prevRowIndex] as Employee;
            if (selectedEmp == null)
                return;

            DragDropEffects dragdropeffects = DragDropEffects.Move;
            if (DragDrop.DoDragDrop(dgEmployee, selectedEmp, dragdropeffects)
                            != DragDropEffects.None)
            {
                //Now This Item will be dropped at new location and so the new Selected Item
                dgEmployee.SelectedItem = selectedEmp;
            }
        }
    }

The updated PreviewMouseLeftButtonDown handler:

void dgEmployee_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        prevRowIndex = GetDataGridItemCurrentRowIndex(e.GetPosition);

        if (prevRowIndex < 0)
            return;

        dgEmployee.SelectedIndex = prevRowIndex;
    }

Not only does it fix your problem but it provides a better user experience. The drag should be initiated when I move the mouse instead of when I press the row.

Next time please link the tutorial that you are using - it will make it much easier for others to reproduce the issue that you are encountering.

Upvotes: 3

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