How to remove the duplicate from list of list?

Question

Hi everyone

I want to ask about this issue

how to remove the duplicate rows from this list

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

I hope to get help and answer

Thanks.

Answer 1

Hi @Asma'a Ahmed Numan

how to remove the duplicate rows from this list List<List<string>> Rows_list = new List<List<string>>();

You can use the Distinct() method to remove the duplicate data.

For example: the first row and third row have the same row, and each row have the duplicate value.

List<List<string>> Rows_list = new List<List<string>>();
 
Rows_list.Add(new List<string> { "Row 1", "Row 2", "Row 3", "Row 2", "Row 3" });  // first row
Rows_list.Add(new List<string> { "Row 21", "Row 22", "Row 23", "Row 22", "Row 23" });  //second row
Rows_list.Add(new List<string> { "Row 1", "Row 2", "Row 3", "Row 2", "Row 3" });   //third row

To remove the duplicate rows (the first row and third row), we can create a ListEqualityComparer class like this (refer this thread):

    public class ListEqualityComparer<T> : IEqualityComparer<List<T>>
    {
        private readonly IEqualityComparer<T> _itemEqualityComparer;

        public ListEqualityComparer() : this(null) { }

        public ListEqualityComparer(IEqualityComparer<T> itemEqualityComparer)
        {
            _itemEqualityComparer = itemEqualityComparer ?? EqualityComparer<T>.Default;
        }

        public static readonly ListEqualityComparer<T> Default = new ListEqualityComparer<T>();

        public bool Equals(List<T> x, List<T> y)
        {
            if (ReferenceEquals(x, y)) return true;
            if (ReferenceEquals(x, null) || ReferenceEquals(y, null)) return false;
            return x.Count == y.Count && !x.Except(y, _itemEqualityComparer).Any();
        }

        public int GetHashCode(List<T> list)
        {
            int hash = 17;
            foreach (var itemHash in list.Select(x => _itemEqualityComparer.GetHashCode(x))
                                         .OrderBy(h => h))
            {
                hash += 31 * itemHash;
            }
            return hash;
        }
    }

Then use the following code to remove the duplicate rows:

var list1 = Rows_list.Distinct(new ListEqualityComparer<string>()).ToList();

After that, if you want to remove duplicate values in each row, use the following code:

var list2 = list1.Select(c => c.Distinct().ToList()).ToList();

So finally, the query statement as below:

var Rows_list2 = Rows_list.Distinct(new ListEqualityComparer<string>()).ToList().Select(c => c.Distinct().ToList()).ToList();

The output like this:

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Best regards,

Dillion