PREVENTING ROW CHANGE IN DATAGRID

Manoj Bhatt

Total Post:154

Points:1086
Posted by  Manoj Bhatt
C#
 1351  View(s)
Ratings:
Rate this:

I have researched this and am stumped: I have a WPF DataGrid, and using an MVVM model. I want to, under certain circumstances, prevent the ability to change a row in the DataGrid. I have researched this and have tried techniques like the one found here.

In practice, this works, however there is an undesirable 'flicker' (it selects the clicked row for a moment then goes back to the previous selection), while this is a close solution I wish there was a more elegant way such as preventing the row change at all in the first place.

I am surprised there is not a SelectionChanging or BeforeSelectionChanged so I could cancel the event from firing; and forcibly preventing the index change in my view model does not seem to make any difference.

How can I do this?

Thank you.

  1. Pravesh Singh

    Post:412

    Points:2888
    Re: preventing row change in datagrid

    Hi Manoj,

    Do you have a CellStyle on your datagrid? For me, the following worked:

    xaml:

    <DataGrid.CellStyle>

        <Style TargetType="{x:Type DataGridCell}">

            <Style.Triggers>

                <Trigger Property="IsSelected" Value="True">

                    <Setter Property="Background" Value="DarkSlateBlue"/>

                    <Setter Property="Foreground" Value="White"/>

                </Trigger>

            </Style.Triggers>

        </Style>

    </DataGrid.CellStyle>

    codebehind:

    private void MyDataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)

    {

        if (e.AddedItems.Count > 0)

        {

            object x = e.AddedItems[0];

            if (x is MyObjectType && x != myViewModel.CurrentItem &&

                myViewModel.ShouldNotDeselectCurrentItem())

            {

                // this will actually revert the SelectedItem correctly, but it won't highlight the correct (old) row.

                this.MyDataGrid.SelectedItem = null;

                this.MyDataGrid.SelectedItem = myViewModel.CurrentItem;

            }

        }

    }

    The point was that the SelectedCellsChanged event fired after the SelectionChanged event -- and in particular, that setting the SelectedItem does not correctly update the SelectedCells which are a read-only property, so more codebehind:

    private void MyDataGrid_SelectedCellsChanged(object sender, SelectedCellsChangedEventArgs e)

    {

        List<DataGridCellInfo> selectedCells = MyDataGrid.SelectedCells.ToList();

        List<MyObjectType> wrongObjects = selectedCells.Select(cellInfo => cellInfo.Item as MyObjectType)

            .Where (myObject => myObject != myViewModel.CurrentItem).Distinct().ToList();

        if (wrongObjects.Count > 0)

        {

            MyDataGrid.UnselectAllCells();

            MyDataGrid.SelectedItem = null;

            MyDataGrid.SelectedItem = myViewModel.CurrentItem;

        }

    }

Answer

NEWSLETTER

Enter your email address here always to be updated. We promise not to spam!