WPF: Change DataGrid cell/row background color dynamically at runtime

Question

I have multiple DataGrids bound to DataTables, which are dynamically created using SQL. Whenever DataTable records change (add, modify, delete), the DataGridCells shall change their background color accordingly (green=new, yellow=modify etc.).

In WinForms I changed DataGridView's background color using _RowPostPaint (code is very simplified):

private void DataGridViewTest_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
{
    DataRow row = (this.Rows[e.RowIndex].DataBoundItem as DataRowView).Row;
    switch (row.RowState)
    {
        case DataRowState.Added:
            myBitmap = new Bitmap(imageList.Images[1]);
            this[0, e.RowIndex].Style.BackColor = CellChangesColorAdded;
            break;
        case DataRowState.Modified:
            string sValOld = row[0, DataRowVersion.Original].ToString();
            string sValNew = row[0].ToString();
            if (sValOld != sValNew)
            {
                this[0, e.RowIndex].Style.BackColor = CellChangesColorMod;
            }
            break;
        case DataRowState.Deleted:
            this[0, e.RowIndex].Style.BackColor = CellChangesColorDel;
            break;
    }
}

I do not want to hardcode column dependencies in XAML as in countless examples like this as they are created at run time and I have many DataGrids in use.

Trying to use DataGrid_CellEditEnding fails, as it does not keep the changes upon sorting etc.:

XAML:

<Window.Resources>
    <Style x:Key="MyStyle" TargetType="{x:Type DataGridCell}">
        <Setter Property="Background" Value="Green" />
    </Style>
</Window.Resources>
<DataGrid x:Name="dataGrid" Grid.Row="4" Grid.ColumnSpan="6"
    ItemsSource="{Binding}"
>
</DataGrid>

.cs:

dataGrid.DataContext = dataTable.DefaultView; // Table filled by SQL query
dataGrid.CellEditEnding += dataGrid_CellEditEnding;

// Problem: Color changes disappear when user sorts DataGrid
    private void dataGrid_CellEditEnding(object sender, DataGridCellEditEndingEventArgs e)
    {
        if (e.EditAction == DataGridEditAction.Commit)
        {
            TextBox tb = e.EditingElement as TextBox;
            DataGridCell cell = tb.Parent as DataGridCell;
            // evaluate row changes and change color accordingly
            //cell.Background = new SolidColorBrush(Colors.Yellow); // set style instead of color
            cell.Style = (Style)this.Resources["MyStyle"]; // color is changed to green, according to defined style
        }
    }

This changes the background color perfectly fine, however the style is not being kept upon sorting the DataGrid etc.

How can I ensure color changes are being kept? In my opinion, the best solution would be to somehow bind DataRows to a helper class and return the respective style upon DataTable changes. However I haven't seen any example for that yet.

Answer 1

For completeness:

If you really intend to change the color at runtime, disregarding MVVM you can for instance use DataGrid_LoadingRow, check for it's DataContext (in this case a DataRowView) and go on from there:

// Changes beeing made to the entire row in this case
private void DgModules_LoadingRow(object sender, DataGridRowEventArgs e)
{
    DataGridRow gridRow = e.Row;
    DataRow row = (gridRow.DataContext as DataRowView).Row;
    switch (row.RowState)
    {
        case DataRowState.Added:
            gridRow.Background = new SolidColorBrush(Colors.Green);
            break;
        case DataRowState.Modified:
            gridRow.Background = new SolidColorBrush(Colors.Yellow);
            break;
        case DataRowState.Deleted:
            gridRow.Background = new SolidColorBrush(Colors.Red);
            break;
    }
}

If you wanna approach this actually using MVVM, go for this solution .