50 lines
1.7 KiB
C#
Executable File
50 lines
1.7 KiB
C#
Executable File
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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namespace MBS.Framework.Collections.Generic
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{
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/// <summary>
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/// Provides a <see cref="T:Dictionary`2" /> that automatically adds or updates a key or value when
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/// it is requested.
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/// </summary>
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/// <typeparam name="TKey">The type of the key part of the dictionary.</typeparam>
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/// <typeparam name="TValue">The type of the value part of the dictionary.</typeparam>
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public class AutoDictionary<TKey, TValue> : Dictionary<TKey, TValue>
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{
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/// <summary>
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/// Retrieves or updates an item with the specified key. If the item does not exist on update,
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/// it will be created. If the item does not exist on retrieval, the value specified for
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/// <paramref name="defaultValue" /> will be returned.
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/// </summary>
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/// <param name="key">The key of the item to retrieve or update.</param>
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/// <param name="defaultValue">The value returned on retrieval when the item with the specified key does not exist.</param>
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/// <returns>The item with the specified key if it exists in this collection; otherwise, defaultValue.</returns>
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public TValue this[TKey key, TValue defaultValue = default(TValue)]
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{
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get
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{
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if (ContainsKey(key))
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{
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// we already contain an item with this key, so return the value accordingly
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return base[key];
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}
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else
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{
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// we do not already contain an item with this key, so create a new value set to the
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// specified default value and return that
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base.Add(key, defaultValue);
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return defaultValue;
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}
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}
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set
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{
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// the .NET Framework Dictionary`2 implementation handles the "add or update" case
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// automatically if a non-existent key is specified
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base[key] = value;
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}
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}
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}
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}
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