这个linq查询出了什么问题?

问题描述

我有一个产品表，其中的标题为字符串.

i have a product table which has a Title as string.

我认为我有

    @using (Html.BeginForm("Serach","Store"))
        {

          <input type="text" name="q" class="searchbox_textbox" />
          <input  type="submit" class="searchbox_btn" />
          }

我的控制器内有

        public ActionResult Serach(string q)
    {
        var result = storeDB.Products
                     .Where(p => p.Title.Contains(q) || string.IsNullOrEmpty(q));


        return View(result);

    }

当我运行页面并输入单词进行搜索时，出现此错误

when i run the page and type a word to search for it give me this error

异常详细信息:System.Data.SqlServerCe.SqlCeException:该函数的指定参数值无效. [参数#= 1，函数名称(如果已知)= isnull]

Exception Details: System.Data.SqlServerCe.SqlCeException: The specified argument value for the function is not valid. [ Argument # = 1,Name of function(if known) = isnull ]

出什么问题了?如果我想向用户显示一条告诉他们您的搜索结果的消息，该怎么办没有任何商品

whats the problem? and what should i do if i want to show users a meesage that tell them your serachdidn't match any product

推荐答案

好吧，您应该使用一些日志记录来查找实际发送到数据库的内容-但就我个人而言，在查询到达之前，我将其拆分了: /p>

Well, you should use some logging to find out what's actually being sent to the database - but personally I'd split the query up before it gets there:

public ActionResult Search(string q)
{
    var result = string.IsNullOrEmpty(q) ? storeDB.Products
                     : storeDB.Products.Where(p => p.Title.Contains(q));

    return View(result);
}

可能是SQL CE支持的SQL方言不支持您正在使用的空性检查-这样就解决了这个问题.

It's possible that the SQL dialect supported by SQL CE doesn't support the check for emptiness that you were using - and this gets round that problem.

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