c# - 无法使用已使用的键(LINQ)添加实体

Question

当我运行以下代码时，出现此错误Cannot add an entity with a key that is already in use.。

表格：


我想念什么？

    private void CopyAllPageObjects(int fromPageID, int toPageID)
    {
        CMSDataContext _db = new CMSDataContext();

        // Copy page objects
        var originalPageObjects = (from x in _db.CMSPageObjects
                                   where x.PageID == fromPageID
                                   select x);

        List<CMSPageObject> newPageObjects = new List<CMSPageObject>();
        foreach (CMSPageObject po in originalPageObjects)
        {
            CMSPageObject newPageObject = new CMSPageObject();
            newPageObject.PageID = toPageID;
            newPageObject.CMSObjectID = po.CMSObjectID;
            newPageObject.Name = po.Name;
            newPageObject.Sorting = po.Sorting;
            newPageObjects.Add(newPageObject);

            // Copy page object attribute values
            var originalPoavs = (from x in _db.CMSPageObjectAttributeValues
                                 where x.CMSPageObjectID == po.ID
                                 select x);

            List<CMSPageObjectAttributeValue> newPoavs = new List<CMSPageObjectAttributeValue>();
            foreach (CMSPageObjectAttributeValue poav in originalPoavs)
            {
                CMSPageObjectAttributeValue newPoav = new CMSPageObjectAttributeValue();
                newPoav.CMSAttributeID = poav.CMSAttributeID;
                newPoav.CMSPageObjectID = newPageObject.ID;
                newPoav.LCID = poav.LCID;
                newPoav.Value = poav.Value;
                newPoavs.Add(newPoav);
            }
            _db.CMSPageObjectAttributeValues.InsertAllOnSubmit(newPoavs);
        }

        _db.CMSPageObjects.InsertAllOnSubmit(newPageObjects);
        _db.SubmitChanges();
    }

Answer 1

似乎您要添加一个对象，而存在另一个具有相同主键的对象。是PageID还是CMSObjectID主键？还是CMSAttributeID？

您可能还希望共享有关数据表外观的更多数据。

更新：添加数据库结构后，我将更仔细地浏览以下行：

newPoav.CMSPageObjectID = newPageObject.ID;

newPageObject.ID可能目前未知，因为您尚未将对象添加到数据库中（我怀疑 是身份）。我认为您可以使用：

newPoav.CMSPageObject = newPageObject