How to show row-number in first column of WPF Datagrid

There might be an easier way to do this but I got it to work by using the GetIndex() method on the DataGridRow class. This returns the index in to the data source so might not be exactly what you’re after.

the xaml

  <Window x:Class="WpfApplication1.MainWindow"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:sys="clr-namespace:System;assembly=mscorlib"
            xmlns:local="clr-namespace:WpfApplication1"
            Title="MainWindow" Height="350" Width="525">
        <DataGrid>
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding RelativeSource={RelativeSource AncestorType=DataGridRow}, Converter={local:RowToIndexConverter}}" />
            </DataGrid.Columns>
            <DataGrid.Items>
                <sys:String>a</sys:String>
                <sys:String>b</sys:String>
                <sys:String>c</sys:String>
                <sys:String>d</sys:String>
                <sys:String>e</sys:String>
            </DataGrid.Items>
        </DataGrid>
    </Window>

and the converter.

public class RowToIndexConverter : MarkupExtension, IValueConverter
{
    static RowToIndexConverter converter;

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        DataGridRow row = value as DataGridRow;
        if (row != null)
            return row.GetIndex();
        else
            return -1;
    }

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

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (converter == null) converter = new RowToIndexConverter();
        return converter;
    }

    public RowToIndexConverter()
    {
    }
}