C#LINQ:如何检索单个结果 [英] c# LINQ: how to retrieve a single result

问题描述

linq的新功能，

使用linq检索单个结果的最简单方法是什么?

whats the simplest way to retrieve a single result using linq?

示例，我的查询

var query =
     from c in db.productInfo
     where c.flavor == "Classic Coke" && c.container == "Can"
     select c.co2Target;

它仅应返回一个带有双精度值的字段.我如何将其拉出查询?过去我曾经使用ExecuteScalar.我如何用linq做到这一点?我想保留其数据类型

it should only return a single field with a double value. how do i pull it out of query? In the past i had used ExecuteScalar. How do i do it with linq? I would like to preserve its data type

更新:

这就是我现在的位置.问题是在这里运行的测试查询返回的是4而不是3.75

Here's where I am now. The problem is that the test query im running here is returning 4 instead of 3.75

var query =
                (from a in db.LUT_ProductInfos
                 where a.flavor == "Classic Coke" && a.Container == "Can"
                 select new { a.co2High }).Single();

            double MyVar = query.co2High.Value;

推荐答案

我认为您的意思是返回一个值，而不是一个记录?您需要执行select new {}如下:

I think you mean return one value, not one record? You would need to do select new {} as follows:

var query =
     from c in db.productInfo
     where c.flavor == "Classic Coke" && c.container == "Can"
     select new { c.co2Target };

然后，如果您只想检索单个记录，则:

Then if you only want to retrieve a single record as well as that:

var query =
     (from c in db.productInfo
     where c.flavor == "Classic Coke" && c.container == "Can"
     select new { c.co2Target }).Single();

检索将按以下步骤进行:

Retrieval would be done as follows:

var query =
         (from c in db.productInfo
         where c.flavor == "Classic Coke" && c.container == "Can"
         select new { c.co2Target }).Single();

double MyVar = query.co2Target;

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