EntityReference(Of TEntity) Class
Represents a related end of an association with a multiplicity of zero or one.
Assembly: System.Data.Entity (in System.Data.Entity.dll)
An EntityReference(Of TEntity) object is returned by a navigation property when the related end has a multiplicity of zero or one. For more information, see Navigation Properties (EDM).
An EntityReference(Of TEntity) object might have a corresponding EntityCollection(Of TEntity) (one-to-many relationship) or EntityReference(Of TEntity) (one-to-one relationship) at the other end of the relationship. When an EntityReference(Of TEntity) and an EntityCollection(Of TEntity) model opposing ends of the same relationship, the integrity of the relationship is maintained at the object level.
This class cannot be inherited.
This example shows how to use the EntityReference(Of TEntity) object to change a relationship between a SalesOrderHeader object and a related Address object that represents the shipping address for the order.
'Define the order and new address IDs. Dim orderId As Integer = 43669 Dim newAddressId As Integer = 26 Using context As New AdventureWorksEntities() Try ' Get the billing address to change to. Dim newAddress As Address = context.Address _ .Where("it.AddressID = @addressId", _ New ObjectParameter("addressId", newAddressId)) _ .First() ' Get the order being changed. Dim order As SalesOrderHeader = context.SalesOrderHeader _ .Where("it.SalesOrderID = @orderId", _ New ObjectParameter("orderId", orderId)).First() ' Load the current billing address. If Not order.Address1Reference.IsLoaded Then order.Address1Reference.Load() End If ' Write the current billing street address. Console.WriteLine("Current street: " _ + order.Address1.AddressLine1) ' Change the billing address. If Not order.Address1.Equals(newAddress) Then order.Address1 = newAddress ' Write the changed billing street address. Console.WriteLine("Changed street: " _ + order.Address1.AddressLine1) End If ' If the address change succeeds, save the changes. context.SaveChanges() ' Write the current billing street address. Console.WriteLine("Current street: " _ + order.Address1.AddressLine1) Catch ex As ApplicationException ' Handle the exception raised in the ShippingAddress_Changed ' handler when the status of the order prevents the ' shipping address from being changed. Don't retry because ' the relationship is in an inconsistent state and calling ' SaveChanges() will result in an UpdateException. Console.WriteLine(ex.ToString()) Catch ex As InvalidOperationException Console.WriteLine(ex.ToString()) End Try End Using
System.Data.Objects.DataClasses.RelatedEnd
System.Data.Objects.DataClasses.EntityReference
System.Data.Objects.DataClasses.EntityReference(Of TEntity)
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.