C# 我如何将 Linq var 转换为 List
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How can i convert Linq var to List
提问by Kartik Patel
I am trying to convert the Linq var to List.my c# code is
我正在尝试将 Linq var 转换为 List.my c# 代码是
private List<HyperlinkInfo> GetHyperlinkByCode()
{
TourInfoBusiness obj = new TourInfoBusiness();
List<HyperlinkInfo> lst = new List<HyperlinkInfo>();
lst = obj.GetAllHyperlink();
//lst = lst.Select(x => x.Attraction).ToList();
var k = lst.Select(x => x.Attraction).Distinct();
}
if you look at the above code till the Line var k = lst.Select(x => x.Attraction).Distinct();is ok Now can i convert var k to List.
如果您查看上面的代码，直到 Line vark = lst.Select(x => x.Attraction).Distinct();正常，现在我可以将 var k 转换为 List。
采纳答案by Sergey Berezovskiy
According to your comments you need single HyperlinInfoobject for each Attractionvalue (which is string). So, use grouping and ToList():
根据您的评论，您需要HyperlinInfo为每个Attraction值（即字符串）使用单个对象。所以，使用分组和ToList()：
private List<HyperlinkInfo> GetHyperlinkByCode()
{
TourInfoBusiness obj = new TourInfoBusiness();
List<HyperlinkInfo> lst = obj.GetAllHyperlink();
return lst.GroupBy(x => x.Attraction) // group links by attraction
.Select(g => g.First()) // select first link from each group
.ToList(); // convert result to list
}
Also you can use morelinqDistinctByextension (available from NuGet):
您也可以使用morelinq DistinctBy扩展（可从 NuGet 获得）：
private List<HyperlinkInfo> GetHyperlinkByCode()
{
TourInfoBusiness obj = new TourInfoBusiness();
List<HyperlinkInfo> lst = obj.GetAllHyperlink();
return lst.DistinctBy(x => x.Attraction).ToList();
}
回答by Habib
Use Enumerable.ToList<TSource> Method. Just Add ToList()at the end of your query or
使用Enumerable.ToList<TSource> Method. 只需ToList()在查询末尾添加或
return k.ToList();
So your method can be:
所以你的方法可以是：
private List<HyperlinkInfo> GetHyperlinkByCode()
{
TourInfoBusiness obj = new TourInfoBusiness();
List<HyperlinkInfo> lst = new List<HyperlinkInfo>();
lst = obj.GetAllHyperlink();
//lst = lst.Select(x => x.Attraction).ToList();
var k = lst.Select(x => x.Attraction).Distinct();
return k.ToList();
}
But x.Attractionshould be HyperLinkInfotype object.
但x.Attraction应该是HyperLinkInfo类型对象。
EDIT:Based on comment it appears that x.Attractionis a string, you need to create object of your class Project.Bll.HyperlinkInfoin select statement and then return that list. Something like:
编辑：根据注释，它似乎x.Attraction是一个字符串，您需要Project.Bll.HyperlinkInfo在 select 语句中创建类的对象，然后返回该列表。就像是：
var k = lst.Select(new Project.Bll.HyperLinkInfo(x => x.Attraction)).Distinct();
Assuming that Project.Bll.HyperlinkInfoconstructor takes a string parameter to return a HyperLinkInfoobject.
假设Project.Bll.HyperlinkInfo构造函数接受一个字符串参数来返回一个HyperLinkInfo对象。
回答by Hamlet Hakobyan
Use this:
用这个：
var k = lst.Select(x => x.Attraction).Distinct().ToList();
Now kis List of x.Attractiontype. If your x.Attractionis string, use this:
现在k是x.Attraction类型列表。如果您x.Attraction是string，请使用以下命令：
List<string> k = lst.Select(x => x.Attraction).Distinct().ToList();
回答by Soner G?nül
回答by Codex
Try this code:
试试这个代码：
return (List<Hyperlink Info>) k
回答by Zaheer Ahmed
try this add DistinctBy of moreLinq:
试试这个添加 DistinctBy 的moreLinq：
public static IEnumerable<TSource> DistinctBy<TSource, TKey>
(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
HashSet<TKey> seenKeys = new HashSet<TKey>();
foreach (TSource element in source)
{
if (seenKeys.Add(keySelector(element)))
{
yield return element;
}
}
}
and call it in your code:
并在您的代码中调用它：
lst.DistinctBy(x => x.Attraction).toList();
