做实体框架关系属性更新

我在WCF web方法中有一些这样的代码，

    List<LocationInRoad> locationInRoad = new List<LocationInRoad>();
    foreach (CarWorkLocationLink locationLink in source.CarWorkLocationLinks)
    {
         locationInRoad.Add(LocationInRoadMapper.MapTo(locationLink.CarWorkLocationType.WorkLocationTypeID));
    }
    destination.LocationInRoad = locationInRoad.ToArray();

有时(可能每周一次)在生产中出现错误，

InvalidOperationException has occured  Message: Collection was modified; enumeration operation may not execute.

所以它似乎在告诉我"来源"。通过在foreach循环中枚举列表，CarWorkLocationLinks的集合已经被修改了一部分。

解释一下，'source'是一个从数据库加载的实体框架实体'CarWorkLocationLinks'是在该实体上定义的，像这样，

    [XmlIgnoreAttribute()]
    [SoapIgnoreAttribute()]
    [DataMemberAttribute()]
    [EdmRelationshipNavigationPropertyAttribute("CarManagerModel", "FK_CarWorkLocationLink_CarDetail", "CarWorkLocationLink")]
    public EntityCollection<CarWorkLocationLink> CarWorkLocationLinks
    {
        get
        {
            return ((IEntityWithRelationships)this).RelationshipManager.GetRelatedCollection<CarWorkLocationLink>("CarManagerModel.FK_CarWorkLocationLink_CarDetail", "CarWorkLocationLink");
        }
        set
        {
            if ((value != null))
            {
                ((IEntityWithRelationships)this).RelationshipManager.InitializeRelatedCollection<CarWorkLocationLink>("CarManagerModel.FK_CarWorkLocationLink_CarDetail", "CarWorkLocationLink", value);
            }
        }
    }

。它是与另一个表的实体关系。所以我想问题是可以一个'EntityCollection'被修改后，它是加载如果在数据库中的东西变化?

基本上，上面的代码适合WCF调用，就像这样，

public APIEntity WCFCall(parameters)
{
    using (EntityContext context = new EntityContext())
    {
        // loading entity (database entity that is)
        // creating API entity (this is a POCO object to control what is exposed over the WCF service)
        // running the loop as shown above on the 'loaded entity' and popluating fields in the poco object
        // returning the poco object
    }
}

所以我不确定为什么我提到的错误应该发生。