Remove duplicates from a List in C#

Question

Remove duplicates from a List in C#

I have a data reader to read the string from database.

I use the List for aggregate the string read from database, but I have duplicates in this string.

Anyone have a quick method for remove duplicates from a generic List in C#?

List<string> colorList = new List<string>();

    public class Lists
    {
        static void Main()
        {
            List<string> colorList = new List<string>();
        }
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            colorList.Add(variableFromDB.ToString());

                    foreach (string color in colorList)
                    {
                      Response.Write(color.ToString().Trim());
                    }
        }
    }

Answer 1

colorList = colorList.Distinct().ToList();

Answer 2

foreach (string color in colorList.Distinct())

Answer 3

Using LINQ:

var distinctItems = colorList.Distinct();

Similar post here: Remove duplicates in the list using linq

Answer 4

IEnumerable<Foo> distinctList = sourceList.DistinctBy(x => x.FooName);

public static IEnumerable<TSource> DistinctBy<TSource, TKey>(
    this IEnumerable<TSource> source,
    Func<TSource, TKey> keySelector)
{
    var knownKeys = new HashSet<TKey>();
    return source.Where(element => knownKeys.Add(keySelector(element)));
}