Generalized method parameters as IList<Topic>

Previously, `ReadOnlyTopicCollection` and `ReadOnlyTopicCollection<T>` had to be constructed explicitly using a `TopicCollection` or `TopicCollection<T>`. To make them more flexible, modified the behavior to accept an `IList<Topic>`. If the `IList<Topic>` is a `TopicCollection<T>` then the underlying collection uses it as is for keying; otherwise, it is converted to a `TopicCollection<T>`. This provides more flexibility, while not changing the normal day-to-day usage of the methods.

Author: JeremyCaney

Ignia.Topics/Collections/ReadOnlyTopicCollection.cs

@@ -4,6 +4,9 @@
 | Project       Topics Library
 \=============================================================================================================================*/
 
+using System.Collections.Generic;
+using System.Diagnostics.Contracts;
+
 namespace Ignia.Topics.Collections {
 
   /*============================================================================================================================
@@ -21,7 +24,23 @@ public class ReadOnlyTopicCollection : ReadOnlyTopicCollection<Topic> {
     ///   Establishes a new <see cref="ReadOnlyTopicCollection"/> based on an existing <see cref="TopicCollection"/>.
     /// </summary>
     /// <param name="innerCollection">The underlying <see cref="TopicCollection"/>.</param>
-    public ReadOnlyTopicCollection(TopicCollection innerCollection) : base(innerCollection) {
+    public ReadOnlyTopicCollection(IList<Topic> innerCollection) : base(innerCollection) {
+    }
+
+    /*==========================================================================================================================
+    | FACTORY METHOD: FROM LIST
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Establishes a new <see cref="ReadOnlyTopicCollection"/> based on an existing <see cref="List{T}"/>.
+    /// </summary>
+    /// <remarks>
+    ///   The <paramref name="innerCollection"/> will be converted to a <see cref="TopicCollection{T}"/>.
+    /// </remarks>
+    /// <param name="innerCollection">The underlying <see cref="TopicCollection{T}"/>.</param>
+    public new static ReadOnlyTopicCollection FromList(IList<Topic> innerCollection) {
+      Contract.Requires(innerCollection != null, "innerCollection should not be null");
+      Contract.Ensures(Contract.Result<ReadOnlyTopicCollection>() != null);
+      return new ReadOnlyTopicCollection(innerCollection);
     }
 
   }

Ignia.Topics/Collections/ReadOnlyTopicCollection{T}.cs

@@ -19,18 +19,18 @@ public class ReadOnlyTopicCollection<T> : ReadOnlyCollection<T> where T : Topic
     /*==========================================================================================================================
     | PRIVATE VARIABLES
     \-------------------------------------------------------------------------------------------------------------------------*/
-    TopicCollection<T> _innerCollection;
+    private readonly            TopicCollection<T>              _innerCollection;
 
     /*==========================================================================================================================
     | CONSTRUCTOR
     \-------------------------------------------------------------------------------------------------------------------------*/
     /// <summary>
-    ///   Establishes a new <see cref="ReadOnlyTopicCollection{T}"/> based on an existing <see cref="TopicCollection{T}"/>.
+    ///   Establishes a new <see cref="ReadOnlyTopicCollection{T}"/> based on an existing <see cref="IList{T}"/>.
     /// </summary>
     /// <param name="innerCollection">The underlying <see cref="TopicCollection{T}"/>.</param>
-    public ReadOnlyTopicCollection(TopicCollection<T> innerCollection) : base(innerCollection) {
+    public ReadOnlyTopicCollection(IList<T> innerCollection) : base(innerCollection) {
       Contract.Requires(innerCollection != null, "innerCollection should not be null");
-      _innerCollection = innerCollection;
+      _innerCollection = innerCollection as TopicCollection<T>?? new TopicCollection<T>(innerCollection);
     }
 
     /*==========================================================================================================================
@@ -57,11 +57,10 @@ public T GetTopic(string key) {
     ///   The <paramref name="innerCollection"/> will be converted to a <see cref="TopicCollection{T}"/>.
     /// </remarks>
     /// <param name="innerCollection">The underlying <see cref="TopicCollection{T}"/>.</param>
-    public static ReadOnlyTopicCollection<T> FromList(List<T> innerCollection) {
+    public static ReadOnlyTopicCollection<T> FromList(IList<T> innerCollection) {
       Contract.Requires(innerCollection != null, "innerCollection should not be null");
       Contract.Ensures(Contract.Result<ReadOnlyTopicCollection<T>>() != null);
-      var topicCollection = new TopicCollection<T>(innerCollection);
-      return new ReadOnlyTopicCollection<T>(topicCollection);
+      return new ReadOnlyTopicCollection<T>(innerCollection);
     }
 
     /*==========================================================================================================================