Dynamic Data many to many templates for EF code first

ManyToMany.ascx.cs

using System;
using System.ComponentModel;
using System.Web.UI;

namespace WebApplication
{
  public partial class ManyToManyField : System.Web.DynamicData.FieldTemplateUserControl
  {
    protected override void OnDataBinding(EventArgs e)
    {
      base.OnDataBinding(e);

      object entity;
      ICustomTypeDescriptor rowDescriptor = Row as ICustomTypeDescriptor;
      if (rowDescriptor != null)
      {
        // Get the real entity from the wrapper
        entity = rowDescriptor.GetPropertyOwner(null);
      }
      else
      {
        entity = Row;
      }

      // Get the collection
      var entityCollection = Column.EntityTypeProperty.GetValue(entity, null);

      // Bind the repeater to the list of children entities
      Repeater1.DataSource = entityCollection;
      Repeater1.DataBind();
    }

    public override Control DataControl
    {
      get
      {
        return Repeater1;
      }
    }

  }
}

ManyToMany_Edit.ascx.cs

using System;
using System.Data.Objects;
using System.ComponentModel;
using System.Collections;
using System.Linq;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.DynamicData;
using System.Collections.Generic;

namespace WebApplication
{
  public partial class ManyToMany_EditField : System.Web.DynamicData.FieldTemplateUserControl
  {
    protected ObjectContext ObjectContext { get; set; }

    public void Page_Load(object sender, EventArgs e)
    {
      // Register for the DataSource's updating event
      EntityDataSource ds = (EntityDataSource)this.FindDataSourceControl();

      ds.ContextCreated += (_, ctxCreatedEventArg) => ObjectContext = ctxCreatedEventArg.Context;

      // This field template is used both for Editing and Inserting
      ds.Updating += new EventHandler<EntityDataSourceChangingEventArgs>(DataSource_UpdatingOrInserting);
      ds.Inserting += new EventHandler<EntityDataSourceChangingEventArgs>(DataSource_UpdatingOrInserting);
    }

    void DataSource_UpdatingOrInserting(object sender, EntityDataSourceChangingEventArgs e)
    {
      MetaTable childTable = ChildrenColumn.ChildTable;

      // Comments assume employee/territory for illustration, but the code is generic

      if (Mode == DataBoundControlMode.Edit)
        ObjectContext.LoadProperty(e.Entity, Column.Name);

      // Get the collection of territories for this employee
      dynamic entityList = Column.EntityTypeProperty.GetValue(e.Entity, null);

      // Go through all the territories (not just those for this employee)
      foreach (dynamic childEntity in childTable.GetQuery(e.Context))
      {

        // Check if the employee currently has this territory
        bool isCurrentlyInList = ListContainsEntity(childTable, entityList, childEntity);

        // Find the checkbox for this territory, which gives us the new state
        string pkString = childTable.GetPrimaryKeyString(childEntity);
        ListItem listItem = CheckBoxList1.Items.FindByValue(pkString);
        if (listItem == null)
          continue;

        // If the states differs, make the appropriate add/remove change
        if (listItem.Selected)
        {
          if (!isCurrentlyInList)
            entityList.Add(childEntity);
        }
        else
        {
          if (isCurrentlyInList)
            entityList.Remove(childEntity);
        }
      }
    }

    protected void CheckBoxList1_DataBound(object sender, EventArgs e)
    {
      MetaTable childTable = ChildrenColumn.ChildTable;

      // Comments assume employee/territory for illustration, but the code is generic

      IEnumerable<object> entityList = null;

      if (Mode == DataBoundControlMode.Edit)
      {
        object entity;
        ICustomTypeDescriptor rowDescriptor = Row as ICustomTypeDescriptor;
        if (rowDescriptor != null)
        {
          // Get the real entity from the wrapper
          entity = rowDescriptor.GetPropertyOwner(null);
        }
        else
        {
          entity = Row;
        }

        // Get the collection of territories for this employee
        entityList = (IEnumerable<object>)Column.EntityTypeProperty.GetValue(entity, null);
      }

      // Go through all the territories (not just those for this employee)
      foreach (object childEntity in childTable.GetQuery(ObjectContext))
      {
        // Create a checkbox for it
        ListItem listItem = new ListItem(
            childTable.GetDisplayString(childEntity),
            childTable.GetPrimaryKeyString(childEntity));

        // Make it selected if the current employee has that territory
        if (Mode == DataBoundControlMode.Edit)
        {
            listItem.Selected = ListContainsEntity(childTable, entityList, childEntity);
        }

        CheckBoxList1.Items.Add(listItem);
      }
    }

    private static bool ListContainsEntity(MetaTable table, IEnumerable<object> list, object entity)
    {
      return list.Any(e => AreEntitiesEqual(table, e, entity));
    }

    private static bool AreEntitiesEqual(MetaTable table, object entity1, object entity2)
    {
      var pks1 = table.GetPrimaryKeyValues(entity1);
      var pks2 = table.GetPrimaryKeyValues(entity2);

      return Enumerable.SequenceEqual(pks1, pks2);
    }

    public override Control DataControl
    {
      get
      {
        return CheckBoxList1;
      }
    }

  }
}