Disable context menu on some DatGrid cells WPF

Question

I have defined a datagrid like this ::

 <cc:PEDataGrid AutoGenerateColumns="False"
               ItemsSource="{Binding Rows}"
               Width="Auto"                
               PreviewMouseRightButtonDown="PEGrid_PreviewMouseRightButtonDown"
               Loaded="CommonPEGrid_Loaded">             
      <wpfkit:DataGrid.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Cut" />
            <MenuItem Header="Copy"/>
            <MenuItem Header="Paste"/>              
        </ContextMenu>
    </wpfkit:DataGrid.ContextMenu>
</cc:PEDataGrid>

This shows contextMenu on every cell when right click is done.
I want to disable context menu for all the cells except headers and also on header for some condition. (I dont want to use DataGridHeaderStyle because of some other problems which I dont want to explain here.)

I have defined a handler for PreviewMouseRightButtonDown on the datagrid and in the handler I am trying to do something like this::

    private void PEGrid_PreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
    {
        DependencyObject depObj = (DependencyObject)e.OriginalSource;

        while ((depObj != null) && !(depObj is DataGridColumnHeader))
        {
            depObj = VisualTreeHelper.GetParent(depObj);
        }

        if (depObj == null)
        {
            return;
        }

        if (depObj is DataGridColumnHeader)
        {
            //some condition here which says whether contextmenu is required on this header

            (depObj as DataGridColumnHeader).ContextMenu = null;
            //the above line is not working!!!!
        }
        else
        {
             (depObj as DataGridCell).ContextMenu = null;
              //the above line not working!!!!
         }
    }

I want to know where am I going wrong!! Please help me regarding this. Also guide me to do in a better way if I am achieving my requirement in a wrong way :)

Answer 1

Hey I Solved it :: My modified code is as follows:::

private void PEGrid_PreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
{
    DependencyObject depObj = (DependencyObject)e.OriginalSource;

    while ((depObj != null) && !(depObj is DataGridColumnHeader))
    {
        depObj = VisualTreeHelper.GetParent(depObj);
    }

    if (depObj == null)
    {
        return;
    }

    if (depObj is DataGridColumnHeader)
    {
          dg.ContextMenu.Visibility = Visibility.Visible;  //works
    }
    else
    {
          dg.ContextMenu.Visibility = Visibility.Collapsed; //works
     }
}

Answer 2

I think this version is way faster and you don't have to set the visibility of the context menu. Just cancel the click event if the click was on the column header.

private void PEGrid_PreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
{
    var depObj = (DependencyObject)e.OriginalSource;
    while ((depObj != null) && !(depObj is DataGridColumnHeader))
    {
        depObj = VisualTreeHelper.GetParent(depObj);
    }
    if (depObj is DataGridColumnHeader)
    {
        e.Handled = true;
    }
}

Answer 3

I have RichTextBox in DataGridCell that is not VisualTree element. My code:

private void dgLog_PreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
    {
        FrameworkContentElement fce = e.OriginalSource as FrameworkContentElement;
        DependencyObject depObj = e.OriginalSource as DependencyObject;
        DataGridCell dgc = null;
        DataGridRow dgr = null;
        try
        {
            while (fce != null && !(fce is DataGridCell))
            {
                depObj = fce.Parent;
                fce = depObj as FrameworkContentElement;
            }
            while (depObj != null && !(depObj is DataGridRow))
            {
                if (depObj is DataGridCell)
                    dgc = depObj as DataGridCell;
                depObj = VisualTreeHelper.GetParent(depObj);
            }
            if (depObj == null)
                return;
            dgr = depObj as DataGridRow;
            if (((LogRecord)dgr.Item).SourceType == "FileMessage" && dgc.Column.DisplayIndex == 1)
                dgLog.ContextMenu = cm_dgLog;
            else
                dgLog.ContextMenu = null;
        }
        catch (Exception ex)
        {
            MessageBox.Show(...);
            TraceHelper.TraceError(ex, GetType());
        }
    }//private void dgLog_PreviewMouseRightButtonDown

LogRecord is the Type of DataGridColumn.Item

Answer 4

    private void dgLog_PreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
    {
        FrameworkContentElement fce = e.OriginalSource as FrameworkContentElement;
        DependencyObject depObj = e.OriginalSource as DependencyObject;
        DataGridCell dgc = null;
        DataGridRow dgr = null;
        try
        {
            while (fce != null && !(fce is DataGridCell))
            {
                depObj = fce.Parent;
                fce = depObj as FrameworkContentElement;
            }
            while (depObj != null && !(depObj is DataGridRow))
            {
                if (depObj is DataGridCell)
                    dgc = depObj as DataGridCell;
                depObj = VisualTreeHelper.GetParent(depObj);
            }
            if (depObj == null)
                return;
            dgr = depObj as DataGridRow;
            if (((LogRecord)dgr.Item).SourceType == "FileMessage" && dgc.Column.DisplayIndex == 1)
                dgLog.ContextMenu = cm_dgLog;
            else
                dgLog.ContextMenu = null;
        }
        catch (Exception ex)
        {
            MessageBox.Show(...);
            TraceHelper.TraceError(ex, GetType());
        }
    }//private void dgLog_PreviewMouseRightButtonDown

Sorry. First attemt was not so good.