Remove Duplicate Items from a Generic List

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If you have a List<string> and want to remove duplicate values before binding it to a control, here's how to do so

C#

var strList = new List<string> 

{ "Jane", "Bill", "jane", "carol", "Carol", "bill" }; 

strList = strList.ConvertAll(low => low.ToLowerInvariant());

var result = from str in strList

        group str by str into grp

        select new { Text = grp.Key};

foreach (var res in result)

{

    DropDownList1.Items.Add(res.Text);

}

VB.NET

    Dim strList = New List(Of String)(New String() _

                {"Jane", "Bill", "jane", "carol", "Carol", "bill"})

    strList = strList.ConvertAll _

    (Function(low) low.ToLowerInvariant())

    Dim result = _

     From str In strList _

     Group str By str Into grp = Group _

     Select New With {Key .Text = str}

    For Each res In result

        DropDownList1.Items.Add(res.Text)

    Next res

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About The Author

Suprotim Agarwal, Developer Technologies MVP (Microsoft Most Valuable Professional) is the founder and contributor for DevCurry, DotNetCurry and SQLServerCurry. He is the Chief Editor of a Developer Magazine called DNC Magazine. He has also authored two Books - 51 Recipes using jQuery with ASP.NET Controls. and The Absolutely Awesome jQuery CookBook.

Follow him on twitter @suprotimagarwal.