Syntax for linq query to List

Question

I am trying to do something like this...

public static List<string> GetAttachmentKeyList()
{
    DataClassesDataContext dc = new DataClassesDataContext();

    List<string> list = from a in dc.Attachments
        select a.Att_Key.ToString().ToList();

    return list;
}

Visual Studio is saying...

Cannot implicitly convert type 'System.Linq.IQueryable>' to 'System.Collections.Generic.List'. An explicit conversion exists (are you missing a cast?)

What is the proper syntax???

score 23 · Accepted Answer · answered Sep 20 '11 at 17:12

23

Give this a try

public static List<string> GetAttachmentKeyList()
{
    DataClassesDataContext dc = new DataClassesDataContext();

    List<string> list = ( from a in dc.Attachments
                          select a.Att_Key.ToString() ).ToList();

    return list;
}

answered Sep 20 '11 at 17:12

Brian Dishaw

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3

+1: Yes, in the original sample the `.ToList()` was called on the string returned by `ToString()`, so the linq expression evaluated to - _something like_ - `IEnumerable>`, not `List` – Binary Worrier Sep 20 '11 at 17:15
THANKS Brian & Praveen for your helpful and incredibly FAST replies!!!! That did the trick. – MalamuteMan Sep 20 '11 at 17:43
1

This is the simplest correction to the code in the question; however [Pedro's answer](https://stackoverflow.com/a/7489012/199364) is more succint. – ToolmakerSteve Dec 27 '17 at 22:31

Pedro Costa · Answer 2 · 2017-03-11T02:18:51.403

12

try this,

public static List<string> GetAttachmentKeyList()
{
    DataClassesDataContext dc = new DataClassesDataContext();

    return dc.Attachments.Select(a=>a.Att_Key).ToList();
}

edited Mar 11 '17 at 02:18

answered Sep 20 '11 at 17:12

Pedro Costa

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+1 - I don't know why one would use the query syntax for such a simple problem. – ChaosPandion Sep 20 '11 at 17:15
1

If there is a better way to do this, would be interested in learning about it. – MalamuteMan Sep 20 '11 at 17:41
1

This is clearly the best answer and should be the accepted answer. – jibbs Jan 25 '17 at 15:38

score 2 · Answer 3 · answered Sep 20 '11 at 17:12

2

I guess it would something like below.

       List<string> list = (from a in dc.Attachments
                             select a.Att_Key.ToString()).ToList<string>();

Hope this helps!!

answered Sep 20 '11 at 17:12

Praveen

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Can we do without the Whole Paranthesis `(from...).ToList()` – Gokul E Jan 04 '14 at 10:58
@GokulE, those parentheses are needed, to know what `ToList` is being applied to - the result of that whole expression. Notice that in the original question, code was attempted, but those parentheses were missing. This applied `ToList` to a single string, inside the `select` clause. OR see Pedro's answer, for a simpler solution. – ToolmakerSteve Dec 27 '17 at 22:27

Syntax for linq query to List

3 Answers3

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