netcore/System.Private.CoreLib/shared/System/Collections/Generic/KeyValuePair.cs

   1 // Licensed to the .NET Foundation under one or more agreements.
   2 // The .NET Foundation licenses this file to you under the MIT license.
   3 // See the LICENSE file in the project root for more information.
   4
   5 using System.ComponentModel;
   6 using System.Text;
   7
   8 namespace System.Collections.Generic
   9 {
  10     // Provides the Create factory method for KeyValuePair<TKey, TValue>.
  11     public static class KeyValuePair
  12     {
  13         // Creates a new KeyValuePair<TKey, TValue> from the given values.
  14         public static KeyValuePair<TKey, TValue> Create<TKey, TValue>(TKey key, TValue value)
  15         {
  16             return new KeyValuePair<TKey, TValue>(key, value);
  17         }
  18
  19         /// <summary>
  20         /// Used by KeyValuePair.ToString to reduce generic code
  21         /// </summary>
  22         internal static string PairToString(object? key, object? value)
  23         {
  24             StringBuilder s = StringBuilderCache.Acquire();
  25             s.Append('[');
  26
  27             if (key != null)
  28             {
  29                 s.Append(key);
  30             }
  31
  32             s.Append(", ");
  33
  34             if (value != null)
  35             {
  36                 s.Append(value);
  37             }
  38
  39             s.Append(']');
  40
  41             return StringBuilderCache.GetStringAndRelease(s);
  42         }
  43     }
  44
  45     // A KeyValuePair holds a key and a value from a dictionary.
  46     // It is used by the IEnumerable<T> implementation for both IDictionary<TKey, TValue>
  47     // and IReadOnlyDictionary<TKey, TValue>.
  48     [Serializable]
  49     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
  50     public readonly struct KeyValuePair<TKey, TValue>
  51     {
  52         private readonly TKey key; // Do not rename (binary serialization)
  53         private readonly TValue value; // Do not rename (binary serialization)
  54
  55         public KeyValuePair(TKey key, TValue value)
  56         {
  57             this.key = key;
  58             this.value = value;
  59         }
  60
  61         public TKey Key => key;
  62
  63         public TValue Value => value;
  64
  65         public override string ToString()
  66         {
  67             return KeyValuePair.PairToString(Key, Value);
  68         }
  69
  70         [EditorBrowsable(EditorBrowsableState.Never)]
  71         public void Deconstruct(out TKey key, out TValue value)
  72         {
  73             key = Key;
  74             value = Value;
  75         }
  76     }
  77 }