Question

Background:

I have a DataGrid whose ItemSource is bound to an ObservableCollection<Dictionary<string, object>> type. The thought behind this is to allow the DataGrid to display a bunch of objects from different sources (This is a log gathering program so the fields all vary from one type of log to the next). I have taken care of the generation of columns through a behavior so I have no knowledge of what the columns will be until runtime.

The Problem:

I want to have a way to show commonalities between the entries based off a field (column) while maintaining the sort order from a different column. To do this I was thinking of going with a color coding system. If the value in a cellA under columnA matched the value of cellB in columnA, the two rows that the cells belong to would get the same unique color for the values found in both cells. The user should also be able to change the column to color code.

I’ve been trying to work with a style to get the desired effect but am having some troubles. Here’s the code in question.

MainWindow.xaml

<DataGrid...>
   <DataGrid.CellStyle>
      <Style TargetType="DataGridCell">
         <Setter Property="Background">
            <Setter.Value>
               <MultiBinding Converter="{StaticResource RowBackgroundConverter}">
                  <MultiBinding.Bindings>
                     <Binding RelativeSource="{RelativeSource Self}"/>
                     <Binding Path="ColumnName"/>
                     <Binding Path="."/>
                  </MultiBinding.Bindings>
               </MultiBinding>
            </Setter.Value>
         </Setter>
      </Style>
   </DataGrid.CellStyle>
</DataGrid>

RowBackgroundConverter

/// <summary>
/// A converter that changes the background of a DataGrid based on a cell value
/// </summary>
public class RowBackgroundConverter : IMultiValueConverter
{

    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (values[0] is DataGridCell)
        {
            DataGridCell cell= (DataGridCell)values[0];
            string columnName = (string)values[1];
            Dictionary<string, object> dataGridValues = (Dictionary<string, object>)values[2];

            // Check the cell's column name and compare it against the desired column name (columnName) Get the index of the value and get the mapped brush. (dataGridValues[columnName]) 

            return new SolidColorBrush(ColorMap.ColorDictionary[0]);

        }

        return SystemColors.AppWorkspaceColor;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

And in my ViewModel I have a ColumnName property for the desired column to color code.

The problem is how can I reach a property in my view model when my multibinding’s context is the data grid cell?

Answer 1

In case I understand your question correctly, you should be able to get to the ColumnName property by setting the relativesource of the binding to the Window.

This assumes that the DataContext of the Window has been set to the ViewModel that contains the ColumnName property.

Something like this should work:

{Binding Path=DataContext.ColumnName, 
         RelativeSource={RelativeSource AncestorType=Window}}