How can i convert Linq var to List

Question

I am trying to convert the Linq var to List.my c# code is

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.

Solution 1

According to your comments you need single HyperlinInfo object for each Attraction value (which is string). So, use grouping and 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 morelinq DistinctBy extension (available from NuGet):

private List<HyperlinkInfo> GetHyperlinkByCode()
{
        TourInfoBusiness obj = new TourInfoBusiness();
        List<HyperlinkInfo> lst = obj.GetAllHyperlink();
        return lst.DistinctBy(x => x.Attraction).ToList();
}

Solution 2

Use Enumerable.ToList<TSource> Method. Just Add ToList() at the end of your query or

return k.ToList();

So your method can be:

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.Attraction should be HyperLinkInfo type object.

EDIT: Based on comment it appears that x.Attraction is a string, you need to create object of your class Project.Bll.HyperlinkInfo in select statement and then return that list. Something like:

var k = lst.Select(new Project.Bll.HyperLinkInfo(x => x.Attraction)).Distinct();

Assuming that Project.Bll.HyperlinkInfo constructor takes a string parameter to return a HyperLinkInfo object.

Solution 3

Use this:

var k = lst.Select(x => x.Attraction).Distinct().ToList();

Now k is List of x.Attraction type. If your x.Attraction is string, use this:

List<string> k = lst.Select(x => x.Attraction).Distinct().ToList();

Comments

[Kartik Patel]

Its not working..The Error Message is "Error 8 Cannot implicitly convert type 'System.Collections.Generic.List<string>' to 'System.Collections.Generic.List<Project.Bll.HyperlinkInfo>'

[Kartik Patel]

Not working....Getting an Error like Cannot implicitly convert type 'System.Collections.Generic.List<string>' to 'System.Collections.Generic.List<Project.Bll.HyperlinkInfo>'

[Kartik Patel]

Not working...getting an error like...Cannot implicitly convert type 'System.Collections.Generic.List<string>' to 'System.Collections.Generic.List<Project.Bll.HyperlinkInfo>'

[Habib]

@KartikPatel, check the edited part, you need to select HyperLinkInfo type object.

[Kartik Patel]

I have to return object of HyperLinkInfo.I cant use List<string?

[Kartik Patel]

still not working and x.Attraction is part of HyperLinkInfo type object.

[Hamlet Hakobyan]

@KartikPatel You have selected x.Attraction which is string. How do you want to convert string in to HyperLinkInfo?