Question

我要做的是模拟将通过网址从另一个系统发送的随机令牌。该其他系统还将在数据库中插入3个值：

ID
IP
当前时间

现在，在另一个时间，客户端访问应用程序时，它必须具有与首次访问它的系统相同的IP和ID，并且时间差必须小于30分钟，否则会话未经过身份验证，并且机器将被限制并发送到错误页面。

我遇到了问题：

当我执行session[] sessionArray = a.ToArray();时，会出现以下错误：

{“FUNCTION cgdimport.DiffMinutes不存在”}

正如WiiMaxx解释的那样：

没有你的错误不存在你的错误 EntityFunctions.DiffMinutes（b.start，DateTime.Now）。因为你的b doesnt包含一个名为DiffMinutes（）的函数

所以我尝试了另一种选择：

ar a = (from b in data.session 
where b.idsession == sessionid 
&& b.ip == clientip 
&& DateTime.Now <= b.start + new TimeSpan(0, 0, 30, 0) 
select b);

但它给了我以下错误：

DbArithmeticExpression参数必须具有数字公共类型。

另一个：

var a = (from b in data.session
                            where b.idsession == sessionid
                            && b.ip == clientip
                            && DateTime.Now <= b.start.AddMinutes(30)
                            select b);

但是出现了这个错误：

LINQ to Entities无法识别方法'System.DateTime AddMinutes（Double）'方法，这个方法无法翻译成商店表达。

public ActionResult SessionController()
    {
        var data = new cgdimportEntities();



        //Request sessionnid from the URL
        if (!Request.QueryString["token"].IsEmpty() && Request.QueryString["token"] != null)
        {
            //Obtain client IP 
            string clientip = HttpContext.Request.UserHostAddress;


            //Request sessionid from url
            string sessionid = Request.QueryString["token"];
            //string sessionid = token;

            //Dummy Test Insert

            var sessionvar = new session {idsession = sessionid, ip = clientip, start = DateTime.Now};

            data.session.Add(sessionvar);


            try { data.SaveChanges(); }

            catch (DbEntityValidationException dbEx)
                {
                foreach (var validationErrors in dbEx.EntityValidationErrors)
                {
                    foreach (var validationError in validationErrors.ValidationErrors)
                    {
                        Trace.TraceInformation("Class: {0}, Property: {1}, Error: {2}", validationErrors.Entry.Entity.GetType().FullName,
                                    validationError.PropertyName, validationError.ErrorMessage);
                    }
                }
                }

            //old code
            //var a = (from b in data.session
                        //where b.idsession == sessionid
                        //&& b.ip == clientip
                        //&& EntityFunctions.DiffMinutes(b.start, DateTime.Now) < 30
                        //select b);
            //old code
            //var a = (from b in data.session 
                       //where b.idsession == sessionid 
                       //&& b.ip == clientip 
                       //&& DateTime.Now <= b.start + new TimeSpan(0, 0, 30, 0) 
                       //select b);

            //new code
              var a = (from b in data.session
                         where b.idsession == sessionid
                         && b.ip == clientip
                         && DateTime.Now <= b.start.AddMinutes(30)
                         select b);


            int count = 0;


            //ERROR HERE! ERROR HERE!
            session[] sessionArray = a.ToArray();


            foreach (var i in sessionArray)
            {
                count++;
            }

            //if 0 rows are counted
            if (count == 0)
            {
                Session["authenticated"] = "false";
                return RedirectToAction("Erro", "Login", new { erro = "No rows counted" });
            }
            //Once all queries are verified, the user is authenticated
            Session["authenticated"] = "true";
            return RedirectToAction("Painel", "Data");
        }
            Session["authenticated"] = "false";
            return RedirectToAction("Erro", "Login", new { erro = "Query is null" });
   }

Answer 1

使用EntityFunctions添加分钟

ar a = (from b in data.session 
 where b.idsession == sessionid 
 && b.ip == clientip 
 && DateTime.Now <= System.Data.Objects.EntityFunctions.AddMinutes(b.start, 30)
 select b);

Answer 2

因为DateTime比较的一个参数是一个常量（关于查询），你可以从查询中删除AddMinutes，这应该删除异常：

DateTime nowMinus30Minutes = DateTime.Now.AddMinutes(-30);

var a = (from b in data.session
         where b.idsession == sessionid
            && b.ip == clientip
            && nowMinus30Minutes <= b.start
         select b);

在MVC3中计算查询数组时出错

2 个答案: