Added support for arbitrary metadata properties on API descriptions

Author: Chris Martinez

src/Microsoft.AspNet.WebApi.Versioning.ApiExplorer/Description/VersionedApiDescription.cs

@@ -1,6 +1,7 @@
 namespace Microsoft.Web.Http.Description
 {
     using System;
+    using System.Collections.Generic;
     using System.Diagnostics;
     using System.Linq.Expressions;
     using System.Web.Http.Description;
@@ -49,6 +50,13 @@ public class VersionedApiDescription : ApiDescription
             }
         }
 
+        /// <summary>
+        /// Gets arbitrary metadata properties associated with the API description.
+        /// </summary>
+        /// <value>A <see cref="IDictionary{TKey, TValue}">collection</see> of arbitrary metadata properties
+        /// associated with the <see cref="VersionedApiDescription">API description</see>.</value>
+        public IDictionary<object, object> Properties { get; } = new Dictionary<object, object>();
+
         static Action<ApiDescription, ResponseDescription> CreateSetResponseDescriptionMutator()
         {
             var api = Expression.Parameter( typeof( ApiDescription ), "api" );

src/Microsoft.AspNet.WebApi.Versioning.ApiExplorer/System.Web.Http/Description/ApiDescriptionExtensions.cs

@@ -47,5 +47,35 @@ public static string GetUniqueID( this ApiDescription apiDescription )
 
             return apiDescription.ID;
         }
+
+        /// <summary>
+        /// Gets a property of the specified type from the API description.
+        /// </summary>
+        /// <typeparam name="T">The <see cref="Type">type</see> of property to retrieve.</typeparam>
+        /// <param name="apiDescription">The <see cref="VersionedApiDescription">API description</see> to get the property from.</param>
+        /// <returns>The value of the property, if present; otherwise, the default value of <typeparamref name="T"/>.</returns>
+        public static T GetProperty<T>( this VersionedApiDescription apiDescription )
+        {
+            Arg.NotNull( apiDescription, nameof( apiDescription ) );
+
+            if ( apiDescription.Properties.TryGetValue( typeof( T ), out object value ) )
+            {
+                return (T) value;
+            }
+
+            return default( T );
+        }
+
+        /// <summary>
+        /// Sets a property of the specified type on the API description.
+        /// </summary>
+        /// <typeparam name="T">The <see cref="Type">type</see> of property to set.</typeparam>
+        /// <param name="apiDescription">The <see cref="VersionedApiDescription">API description</see> to set the property on.</param>
+        /// <param name="value">The value to add or update.</param>
+        public static void SetProperty<T>( this VersionedApiDescription apiDescription, T value )
+        {
+            Arg.NotNull( apiDescription, nameof( apiDescription ) );
+            apiDescription.Properties[typeof( T )] = value;
+        }
     }
 }