I can add a Combobox to a DataGrid using following xmal:

 <local:DataGridTemplateColumn Header="SomeHeader" Width="106" HeaderStyle="{StaticResource headerAlignRightStyle}" CellStyle="{StaticResource cellAlignRightStyle}">
                    <local:DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding SomeProp}" Margin="4"/>
                        </DataTemplate>
                    </local:DataGridTemplateColumn.CellTemplate>
                    <local:DataGridTemplateColumn.CellEditingTemplate>
                        <DataTemplate>
                            <ComboBox 
                              x:Name="SomeCombo"
                              SelectionChanged="SomeCombo_SelectionChanged"
                              ItemsSource="{Binding SomeList}"
                              DisplayMemberPath="Name" 
                              />
                        </DataTemplate>
                    </local:DataGridTemplateColumn.CellEditingTemplate>
                </local:DataGridTemplateColumn>

However what I can't figure out is a sensible way to get the row that was combox is bound to. i.e. when handling the combobox SelectionChanged event I have no way of knowing what what row the combobox belongs to. Particularly I don't know what object in the DataGrid datasource that the combobox is refering to.

Any help would be much appreciated.