如何使用LINQ返回的变量？ [英] How to use returned linq variable?

问题描述

我决定来快速浏览一下事物的LINQ方面，由于只使用直线上升foreach循环反对，但我有一些麻烦它的工作，主要是由于数据类型，我相信。

I've decided to take a quick look into the LINQ side of things, as opposed to just using a straight up foreach loop, but i'm having some trouble getting it to work, mainly due to datatypes i believe.

所以，我这有，到目前为止;

So i've got this, so far;

var selectedSiteType = from sites in siteTypeList
                                   where sites.SiteTypeID == temp
                                   select sites;

siteTypeList是SiteTypes的列表。我试图找到一个特定的一个（我已经谴责与变量温度。

siteTypeList is a list of SiteTypes. I'm trying to find a particular one (Which i've denounced with variable "temp".

我如何再使用这个选择SiteType AS一SiteType？当我尝试，并通过传递selectedSiteType到其他功能，像这样;

How do i then use this selected SiteType AS a SiteType? When i try and pass "selectedSiteType" through to another function, like so;

mSiteTypeSub.EditSitetype(selectedSiteType);

请注意：我试着用提供索引，仿佛selectedSiteType是一个列表/阵列，但没有工作要么，我得到以下错误：

note: I tried with providing an index, as if selectedSiteType was a list / Array, but that didnt work either, i get the following error:

Argument 1: cannot convert from 
'System.Collections.Generic.IEnumerable<DeviceManager_take_2.SiteType>' to 
'DeviceManager_take_2.SiteType' 

我失去了一些东西？也许铸造某种？就像我说我是新来的这一点，我在努力让我的头围绕这一点。机会是我已经得到了整个概念错误，bingbangbosh我已经做了洋相！

Am i missing something? perhaps a cast of some kind? Like i said i'm new to this and am struggling to get my head around this. Chances are i've got the whole concept wrong and bingbangbosh i've made a fool of myself!

干杯提前。

推荐答案

使用首先 / FirstOrDefault /的Single / <一href="http://msdn.microsoft.com/en-us/library/system.linq.enumerable.singleordefault.aspx">SingleOrDefault以获得特定类型的集合的一个项目。

Use First / FirstOrDefault / Single / SingleOrDefault to get a an item of the particular type from the collection.

   var value = selectedSiteType.First(); 
   // returns the first item of the collection

   var value = selectedSiteType.FirstOrDefault(); 
   // returns the first item of the collection or null if none exists

   var value = selectedSiteType.Single(); 
   // returns the only one item of the collection, exception is thrown if more then one exists

   var value = selectedSiteType.SingleOrDefault(); 
   // returns the only item from the collection or null, if none exists. If the collection contains more than one item, an exception is thrown. 

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