Using advWorksContext As New AdventureWorksEntities

    Dim contact As New Contact

    Dim newSalesOrder1 As New SalesOrderHeader
    contact.SalesOrderHeader.Add(newSalesOrder1)

    Dim newSalesOrder2 As New SalesOrderHeader
    contact.SalesOrderHeader.Add(newSalesOrder2)

    Dim relEnds As IEnumerable(Of IRelatedEnd) = _
        CType(contact, IEntityWithRelationships) _
        .RelationshipManager.GetAllRelatedEnds

    Dim relEnd As IRelatedEnd

    For Each relEnd In relEnds
        Dim entityCollection As EntityCollection(Of SalesOrderHeader) = _
            CType(relEnd, EntityCollection(Of SalesOrderHeader))

        Console.WriteLine("EntityCollection count: {0}", entityCollection.Count)

        entityCollection.Remove(newSalesOrder1)

        Dim contains As Boolean = entityCollection.Contains(newSalesOrder1)

        Console.WriteLine("EntityCollection count after one entity has been removed: {0}", _
            entityCollection.Count)

        If Not contains Then
            Console.WriteLine("The removed entity is not in in the collection any more.")
        End If

        relEnd.Add(newSalesOrder1)

        Console.WriteLine("EntityCollection count after an entity has been added again: {0}", _
            entityCollection.Count)
    Next
End Using

using (AdventureWorksEntities advWorksContext =
    new AdventureWorksEntities())
{
    Contact contact = new Contact();

    // Create a new SalesOrderHeader.
    SalesOrderHeader newSalesOrder1 = new SalesOrderHeader();
    // Add SalesOrderHeader to the Contact.
    contact.SalesOrderHeader.Add(newSalesOrder1);

    // Create another SalesOrderHeader.
    SalesOrderHeader newSalesOrder2 = new SalesOrderHeader();
    // Add SalesOrderHeader to the Contact.
    contact.SalesOrderHeader.Add(newSalesOrder2);

    // Get all related ends
    IEnumerable<IRelatedEnd> relEnds =
        ((IEntityWithRelationships)contact)
        .RelationshipManager.GetAllRelatedEnds();

    foreach (IRelatedEnd relEnd in relEnds)
    {
        // Get Entity Collection from related end
        EntityCollection<SalesOrderHeader> entityCollection =
            (EntityCollection<SalesOrderHeader>)relEnd;

        Console.WriteLine("EntityCollection count: {0}",
            entityCollection.Count);
        // Remove the first entity object.
        entityCollection.Remove(newSalesOrder1);

        bool contains = entityCollection.Contains(newSalesOrder1);

        // Write the number of items after one entity has been removed
        Console.WriteLine("EntityCollection count after one entity has been removed: {0}",
            entityCollection.Count);

        if (contains == false)
            Console.WriteLine("The removed entity is not in in the collection any more.");

        //Use IRelatedEnd to add the entity back.
        relEnd.Add(newSalesOrder1);
        Console.WriteLine("EntityCollection count after an entity has been added again: {0}",
            entityCollection.Count);
    }
}