1 files changed, 82 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/Collections/Generic/KeyValuePair.cs b/src/mscorlib/shared/System/Collections/Generic/KeyValuePair.cs
new file mode 100644
index 0000000000..fc51af25f8
--- /dev/null
+++ b/src/mscorlib/shared/System/Collections/Generic/KeyValuePair.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Text;
+
+namespace System.Collections.Generic
+{
+    // Provides the Create factory method for KeyValuePair<TKey, TValue>.
+    public static class KeyValuePair
+    {
+        // Creates a new KeyValuePair<TKey, TValue> from the given values.
+        public static KeyValuePair<TKey, TValue> Create<TKey, TValue>(TKey key, TValue value)
+        {
+            return new KeyValuePair<TKey, TValue>(key, value);
+        }
+
+        /// <summary>
+        /// Used by KeyValuePair.ToString to reduce generic code
+        /// </summary>
+        internal static string PairToString(object key, object value)
+        {
+            StringBuilder s = StringBuilderCache.Acquire();
+            s.Append('[');
+
+            if (key != null)
+            {
+                s.Append(key);
+            }
+
+            s.Append(", ");
+
+            if (value != null)
+            {
+                s.Append(value);
+            }
+
+            s.Append(']');
+
+            return StringBuilderCache.GetStringAndRelease(s);
+        }
+    }
+
+    // A KeyValuePair holds a key and a value from a dictionary.
+    // It is used by the IEnumerable<T> implementation for both IDictionary<TKey, TValue>
+    // and IReadOnlyDictionary<TKey, TValue>.
+    [Serializable]
+    public struct KeyValuePair<TKey, TValue>
+    {
+        private TKey key;       // DO NOT change the field name, it's required for compatibility with desktop .NET as it appears in serialization payload.
+        private TValue value;   // DO NOT change the field name, it's required for compatibility with desktop .NET as it appears in serialization payload.
+
+        public KeyValuePair(TKey key, TValue value)
+        {
+            this.key = key;
+            this.value = value;
+        }
+
+        public TKey Key
+        {
+            get { return key; }
+        }
+
+        public TValue Value
+        {
+            get { return value; }
+        }
+
+        public override string ToString()
+        {
+            return KeyValuePair.PairToString(Key, Value);
+        }
+
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public void Deconstruct(out TKey key, out TValue value)
+        {
+            key = Key;
+            value = Value;
+        }
+    }
+}