Question

我正在使用此查询：

 var result = from r in db.Registrations
              join u in db.UserTypes on r.UserTypeId equals u.UserTypeId
              where r.Email.ToLower()==model.LoginEmail.ToLower() && r.Password.ToLower() == model.Password.ToLower()
              select new { r,u};

如果没有找到记录，我怎么检查？如果是，那么

 if(result == null)
     // no record found
 else
     // record found

Answer 1

您可以使用Any或Count扩展程序：

 if(!result.Any())
///norecord found
else
//record found

使用Count将是：

 if(result.Count()==0)
///norecord found
else
//record found

Answer 2

首先，您为结果分配的只是IQueryable，因此它是查询，您需要先执行它。所以我建议将其重命名为查询，然后执行以下操作：

var query= from r in db.Registrations
           join u in db.UserTypes on r.UserTypeId equals u.UserTypeId
           where r.Email.ToLower()==model.LoginEmail.ToLower() && r.Password.ToLower() == model.Password.ToLower();    
           select new { r,u};

var result = query.FirstOrDefault(); // gives first result or null
if (result == null) {
  // no record
} else {
  // record found and is in result
}

实体框架检查结果为null

2 个答案: