Checks whether a collection contains all the elements of another. - CSharp System.Collections.Generic

CSharp examples for System.Collections.Generic:ICollection

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Description

Checks whether a collection contains all the elements of another.

Demo Code


using System.Linq;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using System;//w w w  .  j  a v a2  s  . c om

public class Main{
        /// <summary>
        /// Checks whether a collection contains all the elements of another.
        /// </summary>
        /// <typeparam name="T">
        /// The type of item in the collection.
        /// </typeparam>
        /// <param name="collection1">
        /// The collection to compare.
        /// </param>
        /// <param name="collection2">
        /// The collection to compare with.
        /// </param>
        /// <param name="comparer">
        /// The comparer.
        /// </param>
        /// <returns>
        /// Returns true if contains all; else false.
        /// </returns>
        public static bool ContainsAll<T>(
            this IEnumerable<T> collection1,
            IEnumerable<T> collection2,
            IEqualityComparer<T> comparer)
        {
            var container = new Dictionary<T, int>(comparer);

            foreach (var item in collection1)
            {
                if (container.ContainsKey(item))
                {
                    container[item]++;
                }
                else
                {
                    container.Add(item, 1);
                }
            }

            foreach (var item in collection2)
            {
                if (container.ContainsKey(item))
                {
                    container[item]--;
                }
                else
                {
                    return false;
                }
            }

            return container.Values.All(c => c == 0);
        }
}

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