1 files changed, 59 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/StrongBox.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/StrongBox.cs
new file mode 100644
index 0000000000..0a1a565f54
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/StrongBox.cs
@@ -0,0 +1,59 @@
+// 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.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Holds a reference to a value.
+    /// </summary>
+    /// <typeparam name="T">The type of the value that the <see cref = "StrongBox{T}"></see> references.</typeparam>
+    public class StrongBox<T> : IStrongBox
+    {
+        /// <summary>
+        /// Gets the strongly typed value associated with the <see cref = "StrongBox{T}"></see>
+        /// <remarks>This is explicitly exposed as a field instead of a property to enable loading the address of the field.</remarks>
+        /// </summary>
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1051:DoNotDeclareVisibleInstanceFields")]
+        public T Value;
+
+        /// <summary>
+        /// Initializes a new StrongBox which can receive a value when used in a reference call.
+        /// </summary>
+        public StrongBox()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref = "StrongBox{T}"></see> with the specified value.
+        /// </summary>
+        /// <param name="value">A value that the <see cref = "StrongBox{T}"></see> will reference.</param>
+        public StrongBox(T value)
+        {
+            Value = value;
+        }
+
+        object IStrongBox.Value
+        {
+            get
+            {
+                return Value;
+            }
+            set
+            {
+                Value = (T)value;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Defines a property for accessing the value that an object references.
+    /// </summary>
+    public interface IStrongBox
+    {
+        /// <summary>
+        /// Gets or sets the value the object references.
+        /// </summary>
+        object Value { get; set; }
+    }
+}