EF 4查询 - 带有多个参数的问题 [英] EF 4 Query - Issue with Multiple Parameters

问题描述

  select * from customers where（@ CustomerName为null或CustomerName = @CustomerName）
  

这对LINQ to SQL有效： p>

  string customerName =XYZ; 
 var results = 
（来自c in ctx.Customers 
其中（customerName == null ||（customerName！= null& c.CustomerName == customerName））
选择c）; 
  

但是上面的查询，当在ADO.NET EF中，不适合我;它应该由客户名称过滤，因为它存在，但它不。而是查询所有的客户记录。现在，这是一个简化的例子，因为我有很多领域，我正在利用这种逻辑。但它从来没有实际过滤，查询所有记录，并导致超时异常。但是最重​​要的是另一个查询做了类似的事情，没有任何问题。

任何想法为什么？似乎像我的错误，还是有解决办法？

谢谢。

解决方案

我还没有弄清楚，但是将其重写为一个proc来解决这个问题，所以这是我的解决方法，就像这样糟糕。

A trick to avoiding filtering by nullable parameters in SQL was something like the following:

select * from customers where (@CustomerName is null or CustomerName = @CustomerName)

This worked well for me in LINQ to SQL:

string customerName = "XYZ";
var results =
   (from c in ctx.Customers 
    where (customerName == null || (customerName != null && c.CustomerName == customerName)) 
    select c);

But that above query, when in ADO.NET EF, doesn't work for me; it should filter by customer name because it exists, but it doesn't. Instead, it's querying all the customer records. Now, this is a simplified example, because I have many fields that I'm utilizing this kind of logic with. But it never actually filters, queries all the records, and causes a timeout exception. But the wierd thing is another query does something similarly, with no issues.

Any ideas why? Seems like a bug to me, or is there a workaround for this? I've since switched to extension methods which works.

Thanks.

解决方案

I still didn't figure it out, but rewriting it as a proc fixed the issue, so that was my workaround, as bad as that is.

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