之前我老大去网上找了一个DAL里面操作数据库的通用类：

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public  class  DALHelper {      public  static  List<T> Search<T>()  where  T : SH_SetBase      {          using  ( var  db =  new  ShopContext())          {              var  dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  return  dbSet.Where(o => !o.IsDelete).ToList();              }              return  dbSet.ToList();          }      }        public  static  List<T> Search<T>(Expression<Func<T,  bool >>  where )  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  return  dbSet.Where(where3.Compile()).ToList();              }              return  dbSet.Where( where ).ToList();          }      }        public  static  List<T> Search<T>(Expression<Func<T,  bool >>  where , PageContent pageContent)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  where  = where3;              }              pageContent.TotalLogs = Count<T>( where );              return  dbSet.Where( where .Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();          }      }        public  static  List<T> Search<T>(Expression<Func<T,  object >> include, Expression<Func<T,  bool >>  where )  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  return  dbSet.Include(include).Where(where3.Compile()).ToList();              }              return  dbSet.Include(include).Where( where ).ToList();          }      }        public  static  List<T> Search<T>(Expression<Func<T,  object >> include, Expression<Func<T,  bool >>  where , PageContent pageContent)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  where  = where3;              }              pageContent.TotalLogs = Count<T>( where );              return  dbSet.Include(include).Where( where .Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();          }      }        public  static  List<T> Search<T>(Expression<Func<T,  bool >>  where , PageContent pageContent, Expression<Func<T,  object >> order,  bool  isAsc)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  where  = where3;              }              pageContent.TotalLogs = Count<T>( where );              if  (isAsc)                  return  dbSet.Where( where .Compile()).OrderBy(order.Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();              else                  return  dbSet.Where( where .Compile()).OrderByDescending(order.Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();          }      }        public  static  List<T> Search<T>(Expression<Func<T,  object >> include, Expression<Func<T,  bool >>  where , PageContent pageContent, Expression<Func<T,  object >> order,  bool  isAsc)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  where  = where3;              }              pageContent.TotalLogs = Count<T>( where );              if  (isAsc)                  return  dbSet.Include(include).Where( where .Compile()).OrderBy(order.Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();              else                  return  dbSet.Include(include).Where( where .Compile()).OrderByDescending(order.Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();          }      }        public  static  List<T> Search<T>(Expression<Func<T,  object >> path1, Expression<Func<T,  object >> path2, Expression<Func<T,  bool >>  where , PageContent pageContent, Expression<Func<T,  object >> order,  bool  isAsc)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  where  = where3;              }              pageContent.TotalLogs = Count<T>( where );              if  (isAsc)                  return  dbSet.Include(path1).Include(path2).Where( where .Compile()).OrderBy(order.Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();              else                  return  dbSet.Include(path1).Include(path2).Where( where .Compile()).OrderByDescending(order.Compile()).Skip((pageContent.PageIndex - 1) * pageContent.PageSize).Take(pageContent.PageSize).ToList();          }      }        public  static  bool  Exist<T>(Expression<Func<T,  bool >>  where )  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  return  dbSet.FirstOrDefault(where3.Compile()) !=  null ;              }              return  dbSet.FirstOrDefault( where .Compile()) !=  null ;          }      }        public  static  int  Count<T>(Expression<Func<T,  bool >>  where )  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  return  dbSet.Count(where3.Compile());              }              return  dbSet.Count( where );          }      }        public  static  decimal  Sum<T>(Expression<Func<T,  bool >>  where , Expression<Func<T,  decimal >> selector)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  return  dbSet.Where(where3.Compile()).Sum(selector.Compile());              }              return  dbSet.Where( where .Compile()).Sum(selector.Compile());          }      }        public  static  int  Sum<T>(Expression<Func<T,  bool >>  where , Expression<Func<T,  int >> selector)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  return  dbSet.Where(where3.Compile()).Sum(selector.Compile());              }              return  dbSet.Where( where .Compile()).Sum(selector.Compile());          }      }        public  static  T SearchObject<T>(Expression<Func<T,  bool >>  where )  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  Expression<Func<T,  bool >> where2 = (o => (o  as  SH_SetBase).IsDelete ==  false );                  var  invokedExpr = Expression.Invoke(where2,  where .Parameters.Cast<Expression>());                  Expression<Func<T,  bool >> where3 = Expression.Lambda<Func<T,  bool >>(Expression.And( where .Body, invokedExpr),  where .Parameters);                  return  dbSet.FirstOrDefault(where3.Compile());              }              return  dbSet.FirstOrDefault( where .Compile());          }      }        public  static  T Find<T>( long  id)  where  T : SH_Base      {          using  (ShopContext db =  new  ShopContext())          {              DbSet<T> dbSet = GetDBSet(db,  typeof (T))  as  DbSet<T>;              if  ( typeof (T).IsSubclassOf( typeof (SH_SetBase)))              {                  SH_SetBase model = dbSet.Find(id)  as  SH_SetBase;                  if  (model !=  null  && !model.IsDelete)                      return  model  as  T;              }              return  dbSet.Find(id)  as  T;          }      }        public  static  bool  Save(SH_Base model)      {          using  (ShopContext db =  new  ShopContext())          {              object  dbSet = GetDBSet(db, model);              if  (model.ID == 0)              {                  CallMethod(dbSet,  "Add" ,  new  object [] { model });              }              else              {                  CallMethod(dbSet,  "Attach" ,  new  object [] { model });                  db.Entry(model).State = EntityState.Modified;              }              if  (model.GetType().IsSubclassOf( typeof (SH_SetBase)))              {                  ((SH_SetBase)model).LastUpdateTime = DateTime.Now;                  ((SH_SetBase)model).IsDelete =  false ;              }              else              {                  ((SH_LogBase)model).LogTime = DateTime.Now;              }              db.SaveChanges();              return  true ;          }      }        public  static  bool  Delete(SH_Base model)      {          using  (ShopContext db =  new  ShopContext())          {              if  (model.GetType().IsSubclassOf( typeof (SH_SetBase)))              {                  ((SH_SetBase)model).LastUpdateTime = DateTime.Now;                  ((SH_SetBase)model).IsDelete =  true ;                  db.Entry(model).State = EntityState.Modified;                  db.SaveChanges();                  return  true ;              }                object  dbSet = GetDBSet(db, model);              CallMethod(dbSet,  "Remove" ,  new  object [] { model });              db.Entry(model).State = EntityState.Modified;              db.SaveChanges();              return  true ;          }      }        private  static  object  GetDBSet(ShopContext db, SH_Base model)      {          string  modelName = ObjectContext.GetObjectType(model.GetType()).Name;          modelName = modelName.Replace( "SH_" ,  "" );          Type type = db.GetType();          PropertyInfo property = type.GetProperty(modelName);          object  dbSet = property.GetValue(db);          return  dbSet;      }        private  static  object  GetDBSet(ShopContext db, Type type)      {          type = ObjectContext.GetObjectType(type);          string  modelName = type.Name;          modelName = modelName.Replace( "SH_" ,  "" );          PropertyInfo property = db.GetType().GetProperty(modelName);          object  dbSet = property.GetValue(db);          return  dbSet;      }        private  static  object  CallMethod( object  obj,  string  methodName,  object [] parms)      {          Type type = obj.GetType();          MethodInfo methodInfo = type.GetMethod(methodName);          return  methodInfo.Invoke(obj, parms);      } }

　　可以看到里面包含了对SH_SetBase的特殊处理，这个有必要解释一下，因为老大之前的设计是数据库表分为两类，一种是记录表（日志表），他们继承自SH_LogBase，一种是姑且说是对象表吧，他们继承自SH_SetBase，然后全部表继承自SH_Base表，为什么要这样设计呢，其中一个原因是对象表里的数据不能真删除，他们一般是有外键的，级联删除的话删除太多了，而且里面的数据也很重要，只能假删除，所以SH_SetBase得有是否删除IsDelete字段，假删除的话那部分数据是不会再取出来的，除了假删除应该还可以禁用，比如冻结账号，冻结后又可以解冻，这就需要是否启用字段IsEnable字段。

　　SH_Base表：

public class SH_Base    {         /// 
        /// 标识，自动增加         /// 
        [Key]        public long ID        {            get;            set;        }        /// 
        /// 备注        /// 
        [Display(Name = "备注")]        public string Summary        {            get;            set;        }    }

　　SH_LogBase表：

public class SH_LogBase : SH_Base    {        private DateTime _logTime = DateTime.Now;        /// 
        /// 记录时间，默认当前时间        /// 
        [Display(Name = "记录时间")]        public DateTime LogTime        {            get { return _logTime; }            set { _logTime = value; }        }    }

　　SH_SetBase表：

public class SH_SetBase : SH_Base    {        /// 
        /// 是否删除，默认未删除        /// 
        [Display(Name = "是否删除")]        public bool IsDelete        {            get;            set;        }        private bool _isEnable = true;        /// 
        /// 是否启用，默认为启用        /// 
        [Display(Name = "是否启用")]        public bool IsEnable        {            get { return _isEnable; }            set { _isEnable = value; }        }        private DateTime _lastUpdateTime = DateTime.Now;        /// 
        /// 最后更新时间，默认当前时间        /// 
        [Display(Name = "最后更新时间")]        public DateTime LastUpdateTime        {            get { return _lastUpdateTime; }            set { _lastUpdateTime = value; }        }    }

　　可我发觉DalHelper太臃肿了，而且里面用到了反射，我一直避免用反射，觉得那货效率比较低。后来看了C#线程内唯一的单例用法。把DalHelper拆分成两个BaseDal和SetBaseDal类，他们继承自IBaseDal类，里面的数据库采用线程内单例模式：

public class DbContextFactory    {        public static ShopContext GetCurrentDbContext()        {            var db = (ShopContext)CallContext.GetData("ShopContext");  //CallContext是一个可提供类似于HashTable的Key-Value键值对存储的缓存对象。

//使用方法：

//1.存储：使用CallContext.SetData(string,object)方法指定缓存指定的对象。

//2.取值：使用CallContext.GetData(string)方法来获取缓存中指定的对象。

//3.清除：使用CallContext.FreeNamedDataSlot(string)方法来移除缓存中指定的对象。

if (db != null) return db;            db = new ShopContext();            CallContext.SetData("ShopContext", db);            return db;        }    }

　　或许有些同志会好奇线程内单例模式有什么好处或者什么用，我这里简单做个测试：

public static ShopContext GetCurrentDbContext()        {            //单例模式：保证线程实例唯一            var db = (ShopContext)CallContext.GetData("ShopContext");            if (db != null)            {                File.AppendAllText("E:\\ShopDb.txt", Thread.CurrentThread.ManagedThreadId + "旧");                return db;            }            File.AppendAllText("E:\\ShopDb.txt", Environment.NewLine + Thread.CurrentThread.ManagedThreadId + "新");            db = new ShopContext();            CallContext.SetData("ShopContext", db);            return db;        }

　　然后运行网站程序，随便乱点打开ShopDb.txt一看

可以看出我每点一次网页链接，控制器的Action接收到请求后就会新建一个线程来处理这次请求，由于我在该线程内一直没有另开线程，所以看到的生成的文件内每次请求就会产生一个新的ShopContext，在单次网页请求内用的都是同一个ShopContext的，这样你可能会说有问题呀，单次网页请求共用一个ShopContext，要是某次数据库请求太耗时，难道后续的操作要一直等待吗，这个问题确实存在，解决的办法就是数据库请求采用异步请求，单个线程共用ShopContext有个好处就是单次请求内只需新建一次ShopContext，不用老在内存中新建这个对象，这样的话可能你会说像线程池一样，搞个ShopContext池不是更好吗，线程要的时候去池中取一个ShopContext出来，不用的时候归还给池，这样ShopContext在内存中新建销毁的次数就可以达到最少次数了，这个我就不研究下去了。

　　接口IBaseDal类：

interface IBaseDal
     
          {        T Find(long id);        T First(Expression
      
       
        > predicate);        T Add(T entity);        bool Update(T entity);        bool Delete(long id);        bool Delete(T entity);        bool Delete(IEnumerable
        
          entities);        bool Exist(Expression
         
          
           > predicate); int Count(Expression
           
            
             > predicate); int Sum(Expression
             
              
               > predicate, Expression
               
                
                 > selector); decimal Sum(Expression
                 
                  
                   > predicate, Expression
                   
                    
                     > selector); IQueryable
                     
                       LoadEntities(); IQueryable
                      
                        LoadEntities(Expression
                       
                        
                         > predicate); IQueryable
                         
                           LoadPageEntities
                          
                           (PageContent page, Expression
                           
                            
                             > predicate, Expression
                             
                              
                               > keySelector, bool isAsc); }
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

　　日志类使用的BaseDal类：

public class BaseDal
     
       : IBaseDal
      
        where T : class , new()    {        public static ShopContext Db        {            get            {                return DbContextFactory.GetCurrentDbContext();            }        }        public virtual T Find(long id)        {            return Db.Set
       
        ().Find(id);        }        public virtual T First(Expression
        
         
          > predicate)        {            return Db.Set
          
           ().FirstOrDefault(predicate); } public virtual T Add(T entity) { Db.Set
           
            ().Add(entity); return entity; } public virtual bool Update(T entity) { Db.Entry(entity).State = EntityState.Modified; return true; } public virtual bool Delete(long id) { return Delete(Find(id)); } public virtual bool Delete(T entity) { Db.Set
            
             ().Remove(entity); return true; } public virtual bool Delete(IEnumerable
             
               entities) { Db.Set
              
               ().RemoveRange(entities); return true; } public virtual bool Exist(Expression
               
                
                 > predicate) { return Db.Set
                 
                  ().Any(predicate); } public virtual int Count(Expression
                  
                   
                    > predicate) { return Db.Set
                    
                     ().Count(predicate); } public virtual int Sum(Expression
                     
                      
                       > predicate, Expression
                       
                        
                         > selector) { try { return Db.Set
                         
                          ().Where(predicate).Sum(selector); } catch { return 0; } } public virtual decimal Sum(Expression
                          
                           
                            > predicate, Expression
                            
                             
                              > selector) { try { return Db.Set
                              
                               ().Where(predicate).Sum(selector); } catch { return 0; } } public virtual IQueryable
                               
                                 LoadEntities() { return Db.Set
                                
                                 ().AsQueryable(); } public virtual IQueryable
                                 
                                   LoadEntities(Expression
                                  
                                   
                                    > predicate) { return Db.Set
                                    
                                     ().Where(predicate); } public virtual IQueryable
                                     
                                       LoadPageEntities
                                      
                                       (PageContent page, Expression
                                       
                                        
                                         > predicate, Expression
                                         
                                          
                                           > keySelector, bool isAsc) { page.TotalItems = Count(predicate); var lst = Db.Set
                                           
                                            ().Where(predicate); lst = isAsc ? lst.OrderBy(keySelector) : lst.OrderByDescending(keySelector); return lst.Skip(page.PageSize * (page.PageIndex - 1)) .Take(page.PageSize); } }
                                           
                                          
                                         
                                        
                                       
                                      
                                     
                                    
                                   
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

　　对象类使用的SetBaseDal类：

public class SetBaseDal
     
       : IBaseDal
      
        where T : SH_SetBase, new()    {        public static ShopContext Db        {            get            {                return DbContextFactory.GetCurrentDbContext();            }        }        public virtual T Find(long id)        {            var t = Db.Set
       
        ().Find(id);            return t.IsDelete ? null : t;        }        public virtual T First(Expression
        
         
          > predicate)        {            return Db.Set
          
           ().Where(o => !o.IsDelete).FirstOrDefault(predicate); } public virtual T Add(T entity) { Db.Set
           
            ().Add(entity); return entity; } public virtual bool Update(T entity) { entity.LastUpdateTime = DateTime.Now; Db.Entry(entity).State = EntityState.Modified; return true; } public virtual bool Delete(long id) { return Delete(Find(id)); } public virtual bool Delete(T entity) { entity.IsDelete = true; entity.LastUpdateTime = DateTime.Now; Db.Entry(entity).State = EntityState.Modified; return true; } public virtual bool Delete(IEnumerable
            
              entities) { foreach (var entity in entities) { Delete(entity); } return true; } public virtual bool Exist(Expression
             
              
               > predicate) { return Db.Set
               
                ().Where(o => !o.IsDelete).Any(predicate); } public virtual int Count(Expression
                
                 
                  > predicate) { return Db.Set
                  
                   ().Where(o => !o.IsDelete).Count(predicate); } public virtual int Sum(Expression
                   
                    
                     > predicate, Expression
                     
                      
                       > selector) { try { return Db.Set
                       
                        ().Where(predicate).Where(o => !o.IsDelete).Sum(selector); } catch { return 0; } } public virtual decimal Sum(Expression
                        
                         
                          > predicate, Expression
                          
                           
                            > selector) { try { return Db.Set
                            
                             ().Where(predicate).Where(o => !o.IsDelete).Sum(selector); } catch { return 0; } } public virtual IQueryable
                             
                               LoadEntities() { return Db.Set
                              
                               ().Where(o => !o.IsDelete); } public virtual IQueryable
                               
                                 LoadEntities(Expression
                                
                                 
                                  > predicate) { return Db.Set
                                  
                                   ().Where(predicate).Where(o => !o.IsDelete); } public virtual IQueryable
                                   
                                     LoadPageEntities
                                    
                                     (PageContent page, Expression
                                     
                                      
                                       > predicate, Expression
                                       
                                        
                                         > keySelector, bool isAsc) { page.TotalItems = Count(predicate); var lst = Db.Set
                                         
                                          () .Where(predicate) .Where(o => !o.IsDelete); lst = isAsc ? lst.OrderBy(keySelector) : lst.OrderByDescending(keySelector); return lst.Skip(page.PageSize * (page.PageIndex - 1)) .Take(page.PageSize); } }
                                         
                                        
                                       
                                      
                                     
                                    
                                   
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

　　里面还有个PageContent类：

public class PageContent    {        public int PageIndex { get; set; }        public int PageSize { get; set; }        public int TotalItems { get; set; }        public int TotalPages        {            get            {                if (PageSize == 0) return 0;                return (TotalItems + PageSize - 1)/PageSize;            }        }    }

 

　　可以看出BaseDal和SetBaseDal之间最大的区别就是BaseDal删除是真删除，SetBaseDal不能真删除，调用删除方法自动执行假删除，而且SetBaseDal获取数据等所有方法都把假删除的数据排除掉了。可能你会问既然假删除的数据都被排除掉了，那他们还有存在的必要吗，当然有必要了，因为除了用户看这些数据，管理人员是可以直接去数据库看的，那就能看到那些被假删除的数据了。

　　写好这BaseDal和SetBaseDal类之后，BLL的类就可以继承自这两个类或者不继承，在类里使用者两个类，设计理念我不在行，貌似不建议直接继承Dal的通用类，而是在BLL定义一个接口，然后实现每个表的该接口，并在该类里引用Dal里的通用类，不过我觉得怎么方便就怎么用吧，何必一定要符合设计理念呢。还有贫血模型也是，按照面向对象理念是不能设计为贫血模型的，因为一个对象必须是完整的，里面的属性就像一个对象的血肉肢体，而里面的方法就像一个对象能够进行的活动，缺少了方法的实体类就像是尸体类，光有肢体不能动，可我还是那句话，怎么方便就怎么用吧，为何一定要面向对象呢，而且我认为光有属性也有好处，当我只需要该对象来传值的时候其实是不需要该对象的行为的，这样的话贫血模型加载到内存中占用的内存就少了些了。当然，这只是我的胡言乱语，大神请直接忽视。。。