EntityFramework4.x/5.0數據庫操作基礎類

本人之前一直寫的都是Java的Dao和Manager不知.NET中的DAL是否也如下,若有不對,請各位園友們指出,謝謝~

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);
    }

　　然后下面該類是基礎操作類,實現了部分CRUD的操作,其余的操作,可以在具體實現類中完成

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>
        /// 保存一條新的記錄
        /// </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>
        /// 修改一個實體
        /// </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>
        /// 修改一個實體,只修改傳入的書包含有該屬性名的字段
        /// </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>
        /// 根據一個實體刪除一個記錄
        /// </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>
        /// 根據主鍵ID刪除一個記錄
        /// </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>
        /// 獲取當前實體的所有集合數據
        /// </summary>
        /// <returns></returns>
        public IList<E> GetDatas()
        {
            using (YzOASysEntities context = new YzOASysEntities())
            {
                return context.Set<E>().ToList();
            }
        }

        /// <summary>
        /// 根據linq條件查詢實體集合數據
        /// </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>
        /// 根據linq條件查詢並返回實體的指定字段的數據集合
        /// </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>
        /// 根據實體ID查找一條記錄
        /// </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)該方法,因為entityframework4.x/5.0是基於DbContext,而4.0是基於ObjectContext,其實DbContext是ObjectContext的上一層封裝,簡化並優化了entityframework的效率,但實際操作還是必須通過ObjectContext完成,又因為DbContext實現了IObjectContextAdapter接口,我們可以通過該接口獲取到ObjectContext對象,那這一切都變的好辦了.通過ObjectContext我們可以獲得當前上下文中的ObjectStateEntry,該對象也就是當前entity的所有狀態所在,我們可以通過設置當期entity的ModifiedProperty達到指定修改某字段的效果.其實我代碼中的

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

　　這段完全可以刪除,因為當我們設置ModifiedProperty時,entityframework已經幫我們自動同步entity的State為Modified了.

 

小弟的C#資歷尚淺,entityframework研究得也不夠透徹,只懂皮毛,若有什么不對的地方,請各位園友,牛人們指出.謝謝~