After previewing the Master /  Detail example I decided Xceed has done a great job of it's continuing expansion but has failed to provide a good readable example for those trying to get their arms around a functioning grid. I put the example on the chopping block and took out all of the items not absolutely necessary to produce a functioning grid. I am posting as I am sure there are others who will benefit from a basic easy to read example. Don't forget to make a copy of your original so you can return to it again when you are ready to expand.

 I have changed just two files.

1. MainPage.xaml

2. MainPage.xaml.cs
 

 Here is the xaml code for MainPage.xaml

<Page x:Class="Xceed.Wpf.DataGrid.Samples.MasterDetail.MainPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:xcdg="http://schemas.xceed.com/wpf/xaml/datagrid"
      xmlns:compModel="clr-namespace:System.ComponentModel;assembly=WindowsBase"
      xmlns:local="clr-namespace:Xceed.Wpf.DataGrid.Samples.MasterDetail">
    <Page.Resources>
        <!--Defined a resource for each converter we want to use in the cell content template-->
        <local:CurrencyConverter x:Key="currencyConverter"/>
        <local:IntegralConverter x:Key="integralConverter"/>
        <local:CustomerConverter x:Key="customerConverter"/>
        <xcdg:StatResultConverter x:Key="statResultConverter"/>
        <xcdg:ThicknessConverter x:Key="thicknessConverter"/>

        <!-- This is the Data Source used in the DataGridControl. It's based on the
           Employees table. -->
        <xcdg:DataGridCollectionViewSource x:Key="cvsEmployees"
                                         Source="{Binding Source={x:Static Application.Current},Path=Employees}"
                                         AutoFilterMode="And"
                                         DistinctValuesConstraint="Filtered">
            <xcdg:DataGridCollectionViewSource.ItemProperties>
                <!--<xcdg:DataGridItemProperty Name="Photo" CalculateDistinctValues="False"/>-->
                <xcdg:DataGridItemProperty Name="FirstName" Title="First Name"/>
                <xcdg:DataGridItemProperty Name="LastName" Title="Last Name"/>
                <xcdg:DataGridItemProperty Name="HireDate" Title="Hire Date"/>
                <xcdg:DataGridItemProperty Name="BirthDate" Title="Birth Date"/>
                <xcdg:DataGridItemProperty Name="Address" CalculateDistinctValues="False"/>
                <xcdg:DataGridItemProperty Name="City"/>
                <xcdg:DataGridItemProperty Name="Country"/>
                <xcdg:DataGridItemProperty Name="Region"/>
                <xcdg:DataGridItemProperty Name="PostalCode" Title="Postal Code"/>
            </xcdg:DataGridCollectionViewSource.ItemProperties>
            <!--DetailDescriptions provide the lookup link between people and orders -->
            <!-- You can comment the below section if desired. Not required for the grid function -->
            <xcdg:DataGridCollectionViewSource.DetailDescriptions>
                <local:EmployeesDetailDescription AutoFilterMode="And"
                                              DistinctValuesConstraint="Filtered">
                    <local:EmployeesDetailDescription.ItemProperties>
                        <xcdg:DataGridItemProperty Name="Photo" CalculateDistinctValues="False"/>
                        <xcdg:DataGridItemProperty Name="FirstName" Title="First Name"/>
                        <xcdg:DataGridItemProperty Name="LastName" Title="Last Name"/>
                    </local:EmployeesDetailDescription.ItemProperties>
                </local:EmployeesDetailDescription>
             <!--DetailDescriptions definitions of relationship and fields used in detail grid -->  
                <xcdg:DataRelationDetailDescription RelationName="EmployeesOrders"
                                                AutoFilterMode="And"
                                                DistinctValuesConstraint="Filtered">
                    <xcdg:DataRelationDetailDescription.ItemProperties>
                        <xcdg:DataGridItemProperty Name="OrderID" CalculateDistinctValues="False"/>
                        <xcdg:DataGridItemProperty Name="ShipVia" Title="Ship via"/>
                        <xcdg:DataGridItemProperty Name="CustomerID" Title="Company"/>
                        <xcdg:DataGridItemProperty Name="Freight"/>
                        <xcdg:DataGridItemProperty Name="OrderDate" Title="Order Date"/>
                        <xcdg:DataGridItemProperty Name="RequiredDate" Title="Required Date"/>
                        <xcdg:DataGridItemProperty Name="ShipCountry" Title="Ship Country"/>
                    </xcdg:DataRelationDetailDescription.ItemProperties>
                   
                     </xcdg:DataRelationDetailDescription>                  
                    </xcdg:DataGridCollectionViewSource.DetailDescriptions>

            <!--End Detail Description -->
           
        </xcdg:DataGridCollectionViewSource>       
       
        <!--The orders detail configuration-->
        <xcdg:DetailConfiguration x:Key="ordersDetailConfiguration"
                             RelationName="EmployeesOrders"
                             Title="Orders"
                             AllowDetailToggle="{Binding Source={x:Static local:MainPageParams.Singleton},Path=AllowDetailToggle}">
            <xcdg:DetailConfiguration.Columns>
                <xcdg:Column FieldName="OrderID"
                         VisiblePosition="1"
                         Width="55"/>

                <xcdg:Column FieldName="ShipVia" VisiblePosition="3"   />

                <xcdg:Column FieldName="CustomerID"
                         VisiblePosition="2"                        
                        
                          /> 
                <xcdg:Column FieldName="Freight"/>  

            </xcdg:DetailConfiguration.Columns>

            <xcdg:DetailConfiguration.DetailConfigurations>
               
                <!--The products detail configuration-->
                <xcdg:DetailConfiguration RelationName="OrdersOrderDetails"
                                      Title="Products"
                                      AllowDetailToggle="{Binding Source={x:Static local:MainPageParams.Singleton},Path=AllowDetailToggle}">
                    <xcdg:DetailConfiguration.Columns>
                        <xcdg:Column FieldName="ProductID" VisiblePosition="2"/>
                        <xcdg:Column FieldName="UnitPrice"/>
                        <xcdg:Column FieldName="Quantity"
                              
                               />
                    </xcdg:DetailConfiguration.Columns>

                    <xcdg:DetailConfiguration.Headers>
                        <DataTemplate>
                            <xcdg:InsertionRow/>
                        </DataTemplate>
                    </xcdg:DetailConfiguration.Headers>
                </xcdg:DetailConfiguration>
            </xcdg:DetailConfiguration.DetailConfigurations>
        </xcdg:DetailConfiguration>
    </Page.Resources>

    <DockPanel>
        <!-- This is the configuration Panel at the Top. -->
        <ContentControl x:Name="parametersHost"
                      DockPanel.Dock="Top"
                      Style="{StaticResource parametersHostStyle}">
            <StackPanel Orientation="Horizontal">
                <GroupBox Header="Master/Detail Actions"
                      Margin="{StaticResource groupBoxMargin}"
                      Padding="{StaticResource groupBoxPadding}">
                    <StackPanel>
                        <CheckBox x:Name="allowDetailToggle"
                            Margin="{StaticResource configItemMargin}"
                            IsChecked="{Binding Source={x:Static local:MainPageParams.Singleton},Path=AllowDetailToggle}"
                            Content="Allow details to be expanded or collapsed"
                            ToolTip="Indicates if details can be expanded or collapsed by the end user."/>

                        <CheckBox x:Name="showOrdersDetail"
                            Margin="{StaticResource configItemMargin}"
                            IsChecked="True"
                            Checked="ShowOrdersDetailChecked"
                            Unchecked="ShowOrdersDetailChecked"
                            Content="Show order/details details"
                            ToolTip="Indicates if the order/details details are visible."/>


                    </StackPanel>
                </GroupBox>
            </StackPanel>
        </ContentControl>

        <!-- The read-only main DataGridControl. -->
        <xcdg:DataGridControl x:Name="grid"
                            CellEditorDisplayConditions="None"
                            ItemsSource="{Binding Source={StaticResource cvsEmployees}}"
                            EditTriggers="BeginEditCommand,ActivationGesture,ClickOnCurrentCell"
                            ItemScrollingBehavior="Immediate"
                            AutoCreateDetailConfigurations="False"
                            AllowDetailToggle="{Binding Source={x:Static local:MainPageParams.Singleton},Path=AllowDetailToggle}">

            <xcdg:DataGridControl.View>
                <!-- In this sample, you can define this resource to specify the default
                 theme this DataGridControl will be in. This is not mandatory, so we
                 use a DynamicResource to silently ignore its absence. -->
                <xcdg:TableView Theme="{DynamicResource defaultTheme}" />
                <!--UseDefaultHeadersFooters="True"-->
            </xcdg:DataGridControl.View>

            <xcdg:DataGridControl.Columns>
                <xcdg:Column FieldName="Photo"
                         Width="45"/>
                <!-- The other columns will be added after these ones and will have default
                 appearance and behavior when they are automatically added upon loading. -->
            </xcdg:DataGridControl.Columns>
        </xcdg:DataGridControl>
    </DockPanel>
</Page>

And here is the code behind - very easy to modify. Just look for the area where I commented the configuration section.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Windows;
using System.Windows.Data;
using System.Collections.Specialized;
using System.Collections;
using System.ComponentModel;
using System.Collections.ObjectModel;
using System.Windows.Controls;

namespace Xceed.Wpf.DataGrid.Samples.MasterDetail
{
  public partial class MainPage : System.Windows.Controls.Page
  {
    public MainPage()
    {
      InitializeComponent();
      this.SetDetailConfigurations();
    }

    private void ShowSubEmployeesDetailChecked( object sender, RoutedEventArgs e )
    {
      this.SetDetailConfigurations();
    }

    private void ShowSubEmployeesEmptyDetailChecked( object sender, RoutedEventArgs e )
    {
      this.SetDetailConfigurations();
    }

    private void ShowOrdersDetailChecked( object sender, RoutedEventArgs e )
    {
      this.SetDetailConfigurations();
    }

    private void SetDetailConfigurations()
    {
      if ( this.grid == null )
        return;

      this.grid.DetailConfigurations.Clear();

      //if ( this.showSubEmployeesDetail.IsChecked.Value )
      //{
      //  if ( this.showSubEmployeesEmptyDetail.IsChecked.Value )
      //  {
      //      // Configuration Removed for simplicity
      //    this.grid.DetailConfigurations.Add( ( DetailConfiguration )this.Resources[ "subEmployeesDetailConfigurationVisibleWhenEmpty" ] );
      //  }
      //  else
      //  {
      //    // Configuration Removed for simplicity
      //    this.grid.DetailConfigurations.Add( ( DetailConfiguration )this.Resources[ "subEmployeesDetailConfigurationNotVisibleWhenEmpty" ] );
      //  }
      //}

      if ( this.showOrdersDetail.IsChecked.Value )
        this.grid.DetailConfigurations.Add( ( DetailConfiguration )this.Resources[ "ordersDetailConfiguration" ] );

      // Collaps all detail and reexpand it.
      List<DataGridContext> dataGridContexts = new List<DataGridContext>( this.grid.GetChildContexts() );

      foreach ( DataGridContext dataGridContext in dataGridContexts )
      {
        dataGridContext.ParentDataGridContext.CollapseDetails( dataGridContext.ParentItem );
        dataGridContext.ParentDataGridContext.ExpandDetails( dataGridContext.ParentItem );
      }
    }
  }
}