將linq中包含子實體的斷開連接的實體更新為sql

Question

在n層應用程序中，linq-to-sql似乎沒有明確的解決方案來更新具有子EntitySet的斷開連接的實體。

我有一些linq-to-sql實體......

public partial class Location : INotifyPropertyChanging, INotifyPropertyChanged
{       
    public int id;      
    public System.Nullable<int> idLocation;     
    public string brandingName;     
    public System.Data.Linq.Binary timeStamp;       
    public EntitySet<LocationZipCode> LocationZipCodes;
}

public partial class LocationZipCode : INotifyPropertyChanging, INotifyPropertyChanged
{
    public string zipcode;      
    public string state;        
    public int idLocationDetail;        
    public int id;      
    public System.Data.Linq.Binary timeStamp;       
    public EntityRef<Location> Location;
}

因此， Location實體將具有LocationZipCodes的EntitySet 。

Location域模型被映射到表示層消耗的視圖模型，然后最終將已更改的視圖模型實體發送回映射回Location域模型。 從那里我更新實體並保存更改。 這是處理程序：

public class ProgramZipCodeManagerHandler : IHttpHandler {
    private LocationsZipCodeUnitOfWork _locationsZipCodeUnitOfWork = new LocationsZipCodeUnitOfWork();

    public void ProcessRequest(HttpContext context) {
        if (context.Request.HttpMethod == "POST") {
            string json = Json.getFromInputStream(context.Request.InputStream);

            if (!string.IsNullOrEmpty(json)) {
                Location newLocation = Json.deserialize<Location>(json);
                if (newLocation != null) {
                    //this maps the location view model from the client to the location domain model
                    var newDomainLocation = new Mapper<Location, DomainLocation>(new DomainLocationMapTemplate()).map(newLocation);

                    if (newDomainLocation.id == 0)
                        _locationsZipCodeUnitOfWork.locationRepository.insert(newDomainLocation);
                    else
                        _locationsZipCodeUnitOfWork.locationRepository.update(newDomainLocation);

                    _locationsZipCodeUnitOfWork.saveChanges(ConflictMode.ContinueOnConflict);

                    var viewModel = new Mapper<DomainLocation, Location>(new LocationMapTemplate()).map(newDomainLocation);
                    context.Response.ContentType = "application/json";
                    context.Response.Write(Json.serialize(viewModel);
                }
            }
        }       
    }
}

這是我的locationRepository的更新方法：

protected System.Data.Linq.Table<T> _table;

public void update(T entity) {
    _table.Attach(entity, true);
    _context.Refresh(RefreshMode.KeepCurrentValues, entity);
}

public void update(T newEntity, T oldEntity) {
    _table.Attach(newEntity, oldEntity);
    _context.Refresh(RefreshMode.KeepCurrentValues, newEntity);
}

我可以看到所有與Location實體直接關聯的記錄都在更新，但public EntitySet<LocationZipCode> LocationZipCodes （ public EntitySet<LocationZipCode> LocationZipCodes ）沒有被更新。

是否有明確的方法來更新具有子EntitySet的斷開連接的實體，該實體也需要更新？ 換句話說，我有一個分離的實體，它有另一個實體的集合。 該集合已更改，我需要在數據庫中更新它。

Answer 1

不......你做不到。

根據您使用的對象附加和分離對象，不會影響相關對象（實體）。

您可以從這里閱讀更多信息：
附加和分離對象

考慮一種情況，其中對象A與集合B相關，集合B填充有1000個值。 您分離A並將其發送到某個遠程處理 - A在B關系中以null發送..現在A被帶回到您的程序 - 無法知道AB null是遠程處理的結果或者是它已經給null了遠程處理。

在使用此答案發布的鏈接中 - 請向下滾動以仔細閱讀標題為：
分離對象的注意事項。

Answer 2

我不太清楚我理解你的問題，但是這里...類似下面的實體對象擴展，也許你將實體重新附加到上下文等，將通過將實體重新附加到對象上下文並適當地設置entitystate來工作。

    /// <summary>
    /// AttachEntityToObjectContext attaches an EntityObject to an ObjectContext
    /// </summary>
    /// <param name="entityWithRelationships">An EntityObject that has relationships</param>
    /// <param name="newContext">The ObjectContext to attach the entity to</param>
    /// <returns>True if the entity has relationships (and therefore the method could succeed). Otherwise false.</returns>
    /// <remarks>Objects are retrieved using one ObjectContext, stored in ViewState and then
    /// an attempt to save them is then made. The save attempt does not save the object. This is because it is a different context which is saving the object.
    /// So the object needs to be detached from its old context, added to the new context and have its EntityState maintained so that it gets saved.</remarks>
    public static bool AttachEntityToObjectContext(this IEntityWithRelationships entityWithRelationships, ObjectContext newContext)
    {
        EntityObject entity = entityWithRelationships as EntityObject;
        if (entity == null)
        {
            return false;
        }

        if (entity.EntityState != EntityState.Detached)
        {
            ObjectContext oldContext = entity.GetContext();
            if (oldContext == null)
            {
                return false;
            }

            if (oldContext != newContext)
            {
                EntityState oldEntityState = entity.EntityState;
                oldContext.Detach(entity);
                newContext.Attach(entity);
                newContext.ObjectStateManager.ChangeObjectState(entity, oldEntityState);
            }
        }

        return true;
    }

    /// <summary>
    /// GetContext gets the ObjectContext currently associated with an entity
    /// </summary>
    /// <param name="entity">An EntityObject</param>
    /// <returns>The ObjectContext which the entity is currently attached to</returns>
    private static ObjectContext GetContext(this IEntityWithRelationships entity)
    {
        if (entity == null)
        {
            throw new ArgumentNullException("entity");
        }

        var relationshipManager = entity.RelationshipManager;

        var relatedEnd = relationshipManager.GetAllRelatedEnds().FirstOrDefault();

        if (relatedEnd == null)
        {
            // No relationships found
            return null;
        }

        var query = relatedEnd.CreateSourceQuery() as ObjectQuery;

        if (query == null)
        {
            // The Entity is Detached
            return null;
        }

        return query.Context;
    }