How to add a cutome row to the end of a DataGrid?

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XAML

WPF

Hello.
I have a problem I have this DataGrid

<DataGrid AutoGenerateColumns="False" 
                          x:Name="detailgrid" 
                          Height="100"
                          ItemsSource="{Binding}"
                          Visibility="Collapsed"
                          ToolTip="This Box shows the order details.">
                    <DataGrid.Columns>
                        <DataGridTextColumn Binding="{Binding ISBN}" 
                                            Header="ISBN" 
                                            x:Name="eisbn"
                                            IsReadOnly="True"/>
                        <DataGridTextColumn Binding="{Binding Quantity}" 
                                            Header="Quantity" 
                                            x:Name="equantity"
                                            IsReadOnly="True"/>
                        <DataGridTextColumn Binding="{Binding Price}" 
                                            Header="Price" 
                                            x:Name="eprice"
                                            IsReadOnly="True"/>
                        <DataGridTextColumn Binding="{Binding Total}" 
                                            Header="Total" 
                                            IsReadOnly="True" 
                                            x:Name="etotal"/>
                        <DataGridTextColumn Binding="{Binding Type}" 
                                            Header="Type" 
                                            x:Name="etype"
                                            IsReadOnly="True"/>
                    </DataGrid.Columns>
                </DataGrid>

It has it's item source What I want to do is to add a row(Footer) that shows the sum of the total inside the grid.