CODEWITHSUNDEEP
c#linq-to-sql
Navyseal
Navyseal

Reputation: 901

Exception while building a dictionary (Linq to SQL)

Well I am trying to build a dictionary using linq to SQL. Not sure how to pick distinct values using the below query. The idea to is fetch the instances of a title between a date.

    GolfitoDataContext db = new GolfitoDataContext();
    var dic = db.GetTable<History>()
            .Select(p => new { p.Title, p.Date }).Where(x => x.Date >= startDateFilter && x.Date <= endDateFilter)
            .AsEnumerable()
            .ToDictionary(k => k.Title, v => v.Date);

I get an exception that "An item with the same key has already been added."

I know its got to do with the "title" being repeated. But not sure how to apply the Distinct() method in the above condition to be able to build the dictionary. If I am doing something wrong, please correct me. Thanks!

Upvotes: 0

Views: 100

Answers (2)

Ehsan
Ehsan

Reputation: 32729

You can do this by using MoreLinQ 

var dic = db.GetTable<History>()
            .Select(p => new { p.Title, p.Date }).Where(x => x.Date >= startDateFilter && x.Date <= endDateFilter)
            .DistinctBy(x=>x.Title) 
            .AsEnumerable()
            .ToDictionary(k => k.Title, v => v.Date);

Upvotes: 1

Marcus
Marcus

Reputation: 8669

This should work:

GolfitoDataContext db = new GolfitoDataContext();
var dic = db.GetTable<History>()
        .Select(p => new { p.Title, p.Date }).Where(x => x.Date >= startDateFilter && x.Date <= endDateFilter)
        .DistinctBy(p => p.Title)
        .AsEnumerable()
        .ToDictionary(k => k.Title, v => v.Date);

Upvotes: 3

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