Mega Code Archive
Group the collection using a function which returns the key
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#region License
// Copyright 2006 James Newton-King
// http://www.newtonsoft.com
//
// This work is licensed under the Creative Commons Attribution 2.5 License
// http://creativecommons.org/licenses/by/2.5/
//
// You are free:
// * to copy, distribute, display, and perform the work
// * to make derivative works
// * to make commercial use of the work
//
// Under the following conditions:
// * You must attribute the work in the manner specified by the author or licensor:
// - If you find this component useful a link to http://www.newtonsoft.com would be appreciated.
// * For any reuse or distribution, you must make clear to others the license terms of this work.
// * Any of these conditions can be waived if you get permission from the copyright holder.
#endregion
using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
namespace MySpace.Common.IO.JSON.Utilities
{
internal delegate T Func<A0, T>(A0 arg0);
internal static class CollectionUtils
{
/// <summary>
/// Group the collection using a function which returns the key.
/// </summary>
/// <param name="source">The source collection to group.</param>
/// <param name="keySelector">The key selector.</param>
/// <returns>A Dictionary with each key relating to a list of objects in a list grouped under it.</returns>
public static Dictionary<K, List<V>> GroupBy<K, V>(ICollection<V> source, Func<V, K> keySelector)
{
if (keySelector == null)
throw new ArgumentNullException("grouper");
Dictionary<K, List<V>> groupedValues = new Dictionary<K, List<V>>();
foreach (V value in source)
{
// using delegate to get the value's key
K key = keySelector(value);
List<V> groupedValueList;
// add a list for grouped values if the key is not already in Dictionary
if (!groupedValues.TryGetValue(key, out groupedValueList))
{
groupedValueList = new List<V>();
groupedValues.Add(key, groupedValueList);
}
groupedValueList.Add(value);
}
return groupedValues;
}
}
}
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