Convert the enumerable to a Dictionary using the keySelector to extract keys from values and the specified comparer. Fast paths for array and IList of T. - CSharp System.Collections.Generic

CSharp examples for System.Collections.Generic:IList

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Description

Convert the enumerable to a Dictionary using the keySelector to extract keys from values and the specified comparer. Fast paths for array and IList of T.

Demo Code

// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
using System.Linq;
using System.Diagnostics.Contracts;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using System;//from w w w .  j a v  a  2  s.co  m

public class Main{
        /// <summary>
        /// Convert the enumerable to a Dictionary using the keySelector to extract keys from values and the specified comparer. Fast paths for array and IList of T.
        /// </summary>
        public static Dictionary<TKey, TValue> ToDictionaryFast<TKey, TValue>(this IEnumerable<TValue> enumerable, Func<TValue, TKey> keySelector, IEqualityComparer<TKey> comparer)
        {
            Contract.Assert(enumerable != null);
            Contract.Assert(keySelector != null);

            TValue[] array = enumerable as TValue[];
            if (array != null)
            {
                return ToDictionaryFast(array, keySelector, comparer);
            }
            IList<TValue> list = enumerable as IList<TValue>;
            if (list != null)
            {
                return ToDictionaryFastNoCheck(list, keySelector, comparer);
            }
            Dictionary<TKey, TValue> dictionary = new Dictionary<TKey, TValue>(comparer);
            foreach (TValue value in enumerable)
            {
                dictionary.Add(keySelector(value), value);
            }
            return dictionary;
        }
        /// <summary>
        /// Convert the list to a Dictionary using the keySelector to extract keys from values and the specified comparer. Optimized for IList of T input with fast path for array.
        /// </summary>
        public static Dictionary<TKey, TValue> ToDictionaryFast<TKey, TValue>(this IList<TValue> list, Func<TValue, TKey> keySelector, IEqualityComparer<TKey> comparer)
        {
            Contract.Assert(list != null);
            Contract.Assert(keySelector != null);

            TValue[] array = list as TValue[];
            if (array != null)
            {
                return ToDictionaryFast(array, keySelector, comparer);
            }
            return ToDictionaryFastNoCheck(list, keySelector, comparer);
        }
        /// <summary>
        /// Convert the array to a Dictionary using the keySelector to extract keys from values and the specified comparer. Optimized for array input.
        /// </summary>
        public static Dictionary<TKey, TValue> ToDictionaryFast<TKey, TValue>(this TValue[] array, Func<TValue, TKey> keySelector, IEqualityComparer<TKey> comparer)
        {
            Contract.Assert(array != null);
            Contract.Assert(keySelector != null);

            Dictionary<TKey, TValue> dictionary = new Dictionary<TKey, TValue>(array.Length, comparer);
            for (int i = 0; i < array.Length; i++)
            {
                TValue value = array[i];
                dictionary.Add(keySelector(value), value);
            }
            return dictionary;
        }
}

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