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问题描述

我正在使用VS2012和DBContext(实体框架)。



以下查询引发异常



客户托管;

  
使用(var context = new MiniNorthwindContext()){
cust =(从C中的c在context.Customers
其中c.CustomerName.Contains(SN)
select c) .SingleOrDefault();
}

当我运行它时会引发以下错误:序列包含多于一个元素。



如果我将其替换为

  ; 
使用(var context = new MiniNorthwindContext()){
cust =(from c in context.Customers
where c.CustomerName ==SN Software
select c)的SingleOrDefault();
}

然后它通过


解决方案

可以执行以下三种操作之一:




  • 如果没有结果,返回默认值;

  • 如果有一个结果;返回它;

  • 如果有多个结果,则会抛出该异常。



所以您的查询匹配多行。


I'm using VS2012, and the DBContext (Entity Framework).

The following query throws an exception

Customer cust;
using (var context = new MiniNorthwindContext()) {
    cust = (from c in context.Customers
            where c.CustomerName.Contains("SN")
            select c).SingleOrDefault();
}

When I run it, it throws the following error: "Sequence contains more than one element".

If I replace it with

Customer cust;
using (var context = new MiniNorthwindContext()) {
    cust = (from c in context.Customers
            where c.CustomerName == "SN Software"
            select c).SingleOrDefault();
}

Then it passes.

What could I be doing wrong.

解决方案

SingleOrDefault can do one of three things:

  • if there are no results, return the default;
  • if there is one result; return it;
  • if there is more than one result, it throws that exception.

So your query is matching more than one row.

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08-19 14:22