/// 
        /// 直接获取特定一个或者多个字段的值        /// 多个字段需要声明Model        /// var s=  testDal.GetScalar
     
      (m=>m.Code== "02018",m=>new { m.Name,m.Code });        /// var a = s.Name;        /// 
     
        /// 
            ///         ///         /// 
            public T GetScalar
    
     (Expression
     
      
       > predicate, Expression
       
        
         > scalar)        {            if (predicate == null)            {                return dbcontext.Set
         
          ().AsNoTracking().Select(scalar).FirstOrDefault(); } else { return dbcontext.Set
          
           ().AsNoTracking().Where(predicate).Select(scalar).FirstOrDefault(); } }