关于Entity Framework中的Attached报错的完美解决方案-白红宇的个人博客

发布日期：2021-05-09 09:35:01 浏览次数：12 分类：博客文章

本文共 6135 字，大约阅读时间需要 20 分钟。

��Entity Framework��CRUD��NoTracking��

//������DB First������������������������aTestEntities db = new aTestEntities();db.Companies.MergeOption = MergeOption.NoTracking;//������CODE First���Model First������������������������aTestEntities db = new aTestEntities();db.Companies.AsNoTracking();

��NoTracking��CUD��

��

��NoTracking��Detached,��CRD��Attach��CRD��Detached��Attach��

��Attach��Attach��Attached��Attach��EF��IsAttached��

��DB First��EntityObject��EntityObject.EntityKey��

///         /// ������entity������������Attached        /// 
        ///         /// 
            public bool IsAttached
    
     (TEntity entity) where TEntity : EntityObject        {            ObjectStateEntry entry = null;            if (dbContext.ObjectStateManager.TryGetObjectStateEntry(entity.EntityKey, out entry))            {                if (entry.State != EntityState.Detached)                {                    return true;                }            }            return false;        }

��Model First��Code First��EntityObject��IEntityWithId��,��

public interface IEntityWithId    {        Guid Id { get; set; }    }    public class EntityClass : IEntityWithId    {        Guid Id { get; set; }        //...������������    }///         /// ������entity������������Attached        /// 
        /// 
            ///         /// 
            public bool IsAttached
    
     (TEntity entity) where TEntity : IEntityWithId        {            TEntity localEntity = dbContext.Set
     
      ().Local.Where(t => t.Id == entity.Id).FirstOrDefault();            if (localEntity != null)            {                if (dbContext.Entry(localEntity).State != EntityState.Detached)                {                    return true;                }            }            return false;        }

��Model First��Code First��IsAttached��VS Debug��EntityWrapperWithoutRelationships<TEntity>��_entityWrapper��EntityWrapper��EntityKey��EntityObject.EntityKey��EntityKey��EntityWrapperWithoutRelationships��EntityWrapper��internal,��

///         /// ������entity������������Attached        /// 
        ///         /// 
            private bool IsAttached(TEntity entity)        {            var objectContext = ((IObjectContextAdapter)this.baseContext).ObjectContext;            ObjectStateEntry entry = null;            if (objectContext.ObjectStateManager.TryGetObjectStateEntry(GetEntityKey(entity), out entry))            {                if (entry.State != EntityState.Detached)                {                    return true;                }            }            return false;        }        ///         /// ���������������������������������EntityKey        /// 
        ///         /// 
            private EntityKey GetEntityKey(TEntity entity)        {            var entityWrapper = entity.GetType().GetField("_entityWrapper").GetValue(entity);//������������_entityWrapper������            var entityWrapperType = entityWrapper.GetType();//���������������������            var entityKey = entityWrapperType.GetProperty("EntityKey").GetValue(entityWrapper, null);//������EntityKey������������            return (EntityKey)entityKey;        }

��IsAttached��Attach��IsAttached��Attached��Attach��

public virtual void Update(TEntity entity, bool autoCommit = false)        {            this.ValidateEntity(entity, false);            if (!this.IsAttached(entity))            {                this.objectSet.Attach(entity);                this.baseContext.Entry(entity).State = EntityState.Modified;            }            if (autoCommit)            {                this.Commit();            }        }        public virtual void Remove(TEntity entity, bool autoCommit = false)        {            if (!this.IsAttached(entity))            {                this.objectSet.Attach(entity);            }            this.objectSet.Remove(entity);            if (autoCommit)            {                this.Commit();            }        }

上一篇：关于C# Winform DataGridView 设置DefaultCellStyle无效的原因与解决方案

下一篇：实现winform DataGridView控件判断滚动条是否滚动到当前已加载的数据行底部

发表评论

关于作者

喝酒易醉，品茶养心，人生如梦，品茶悟道，何以解忧？唯有杜康！

-- 愿君每日到此一游！

发表评论

最新留言

关于作者

推荐文章