EntityFramework4.x/5.0数据库操作基础类

本人之前一直写的都是Java的Dao和Manager不知.NET中的DAL是否也如下,若有不对,请各位园友们指出,谢谢~

先放上接口

public interface IDAL<PK, E>
        where PK : struct
        where E : class, new()
    {
        
        int Save(E entity);
        int Update(E entity);
        int Update(E entity, string[] propertys);
        int Delete(E entity);
        int Delete(PK id);
        IList<E> GetDatas();
        IList<E> GetDatas(Expression<Func<E, bool>> predicate);
        IList<T> GetDatas<T>(Expression<Func<E, bool>> predicate, Expression<Func<E, T>> selector);
        E GetById(PK id);

        int ExecuteRawCommand(string sql, params object[] parameters);
        IList<E> SqlQuery(string sql, params object[] parameters);
    }

　　然后下面该类是基础操作类,实现了部分CRUD的操作,其余的操作,可以在具体实现类中完成

public abstract class AbstractBaseDAL<PK, E> : IDAL<PK, E>
        where PK : struct
        where E : class, new()
    {

        public const string PK_ID = "Id";

        public Type GetEntityType()
        {
            return typeof(E);
        }

        
        /// <summary>
        /// 保存一条新的记录
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public int Save(E entity)
        {
            int changeCount = 0;
            using (TransactionScope transaction = new TransactionScope(TransactionScopeOption.Required))
            {
                using (YzOASysEntities context = new YzOASysEntities())
                {
                    context.Set<E>().Add(entity);
                    changeCount = context.SaveChanges();

                    if (changeCount > 0)
                        transaction.Complete();
                }
            }
            return changeCount;
        }

        /// <summary>
        /// 修改一个实体
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public int Update(E entity)
        {
            int changeCount = 0;
            using(TransactionScope transaction = new TransactionScope (TransactionScopeOption.Required))
            {
                using (YzOASysEntities context = new YzOASysEntities())
                {
                    context.Set<E>().Attach(entity);
                    
                    if (context.Entry<E>(entity).State == EntityState.Unchanged)
                        context.Entry<E>(entity).State = EntityState.Modified;
                    changeCount = context.SaveChanges();
                    if (changeCount > 0)
                        transaction.Complete();
                }
            }
            return changeCount;
        }

        /// <summary>
        /// 修改一个实体,只修改传入的书包含有该属性名的字段
        /// </summary>
        /// <param name="entity"></param>
        /// <param name="propertys"></param>
        /// <returns></returns>
        public int Update(E entity, string[] propertys)
        {
            int changeCount = 0;
            using(TransactionScope transaction = new TransactionScope (TransactionScopeOption.Required))
            {
                using (YzOASysEntities context = new YzOASysEntities())
                {
                    context.Set<E>().Attach(entity);
                    
                    IObjectContextAdapter objectContextAdatper = context;
                    ObjectContext objectContext = objectContextAdatper.ObjectContext;
                    ObjectStateEntry ose = objectContext.ObjectStateManager.GetObjectStateEntry(entity);
                    foreach (string property in propertys)
                    {
                        ose.SetModifiedProperty(property);
                    }

                    if (context.Entry<E>(entity).State == EntityState.Unchanged)
                        context.Entry<E>(entity).State = EntityState.Modified;
                    changeCount = context.SaveChanges();
                    if (changeCount > 0)
                        transaction.Complete();
                }
            }
            return changeCount;
            
        }

        /// <summary>
        /// 根据一个实体删除一个记录
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public int Delete(E entity)
        {
            int changeCount = 0;
            using(TransactionScope transaction = new TransactionScope (TransactionScopeOption.Required))
            {
                using (YzOASysEntities context = new YzOASysEntities())
                {
                    context.Set<E>().Attach(entity);
                    if (context.Entry<E>(entity).State == EntityState.Unchanged)
                        context.Entry<E>(entity).State = EntityState.Deleted;
                    context.Set<E>().Remove(entity);
                    try
                    {
                        changeCount = context.SaveChanges();
                    }
                    catch (DbUpdateConcurrencyException ex)
                    {
 
                    }
                    if (changeCount > 0)
                        transaction.Complete();
                }
            }
            return changeCount;
        }

        /// <summary>
        /// 根据主键ID删除一个记录
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public int Delete(PK id)
        {
            int changeCount = 0;
            using (TransactionScope transaction = new TransactionScope(TransactionScopeOption.Required))
            {
                using (YzOASysEntities context = new YzOASysEntities())
                {
                    E e = new E();
                    PropertyInfo pi =  e.GetType().GetProperty(PK_ID);
                    pi.SetValue(e, id, null);
                    context.Set<E>().Attach(e);
                    if (context.Entry<E>(e).State == EntityState.Unchanged)
                        context.Entry<E>(e).State = EntityState.Deleted;
                    context.Set<E>().Remove(e);

                    try
                    {
                        changeCount = context.SaveChanges();
                    }
                    catch (DbUpdateConcurrencyException ex)
                    {
                        
                    }
                    if (changeCount > 0)
                        transaction.Complete();
                }
            }
            return changeCount;
        }

        /// <summary>
        /// 获取当前实体的所有集合数据
        /// </summary>
        /// <returns></returns>
        public IList<E> GetDatas()
        {
            using (YzOASysEntities context = new YzOASysEntities())
            {
                return context.Set<E>().ToList();
            }
        }

        /// <summary>
        /// 根据linq条件查询实体集合数据
        /// </summary>
        /// <param name="predicate"></param>
        /// <returns></returns>
        public IList<E> GetDatas(Expression<Func<E, bool>> predicate)
        {
            using (YzOASysEntities context = new YzOASysEntities())
            {
                return context.Set<E>().Where(predicate).ToList();
            }
        }

        /// <summary>
        /// 根据linq条件查询并返回实体的指定字段的数据集合
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="predicate"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public IList<T> GetDatas<T>(Expression<Func<E, bool>> predicate, Expression<Func<E, T>> selector)
        {
            using (YzOASysEntities context = new YzOASysEntities())
            {
                return context.Set<E>().Where(predicate).Select(selector).ToList();
            }
        }

        /// <summary>
        /// 根据实体ID查找一条记录
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public E GetById(PK id)
        {
            using (YzOASysEntities context = new YzOASysEntities())
            {
                return context.Set<E>().Find(id);
            }
        }

        /// <summary>
        /// 操作原生SQL
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public int ExecuteRawCommand(string sql, params object[] parameters)
        {
            using (TransactionScope transaction = new TransactionScope(TransactionScopeOption.Required))
            {
                using (YzOASysEntities context = new YzOASysEntities())
                {
                    return context.Database.ExecuteSqlCommand(sql, parameters);
                }
            }
        }

        public IList<E> SqlQuery(string sql, params object[] parameters)
        {
            using (YzOASysEntities context = new YzOASysEntities())
            {
                return context.Database.SqlQuery<E>(sql, parameters).ToList();
            }
        }
    }

　　值得注意的是public int Update(E entity, string[] propertys)该方法,因为entityframework4.x/5.0是基于DbContext,而4.0是基于ObjectContext,其实DbContext是ObjectContext的上一层封装,简化并优化了entityframework的效率,但实际操作还是必须通过ObjectContext完成,又因为DbContext实现了IObjectContextAdapter接口,我们可以通过该接口获取到ObjectContext对象,那这一切都变的好办了.通过ObjectContext我们可以获得当前上下文中的ObjectStateEntry,该对象也就是当前entity的所有状态所在,我们可以通过设置当期entity的ModifiedProperty达到指定修改某字段的效果.其实我代码中的

if (context.Entry<E>(entity).State == EntityState.Unchanged)
                        context.Entry<E>(entity).State = EntityState.Modified;

　　这段完全可以删除,因为当我们设置ModifiedProperty时,entityframework已经帮我们自动同步entity的State为Modified了.

小弟的C#资历尚浅,entityframework研究得也不够透彻,只懂皮毛,若有什么不对的地方,请各位园友,牛人们指出.谢谢~