Core.ObjectsResolution - cleanup + start making things public

src/Umbraco.Core/ObjectResolution/SingleObjectResolverBase.cs

@@ -3,49 +3,100 @@
 namespace Umbraco.Core.ObjectResolution
 {
 	/// <summary>
-	/// A Resolver to return and set a Single registered object.
+	/// The base class for all single-object resolvers.
 	/// </summary>
-	/// <typeparam name="TResolved"></typeparam>
-	/// <typeparam name="TResolver"> </typeparam>
+	/// <typeparam name="TResolver">The type of the concrete resolver class.</typeparam>
+	/// <typeparam name="TResolved">The type of the resolved object.</typeparam>
 	/// <remarks>
-	/// Used for 'singly' registered objects. An example is like the MVC Controller Factory, only one exists application wide and it can
-	/// be get/set.
+	/// Resolves "single" objects ie objects for which there is only one application-wide instance, such as the MVC Controller factory.
 	/// </remarks>
-	internal abstract class SingleObjectResolverBase<TResolver, TResolved> : ResolverBase<TResolver>
+	public abstract class SingleObjectResolverBase<TResolver, TResolved> : ResolverBase<TResolver>
 		where TResolved : class
 		where TResolver : class
 	{
 		TResolved _resolved;
 		readonly bool _canBeNull;
 
+		// NOTE - we're not freezing resolution here so it is potentially possible to change the instance at any time?
+
+		#region Constructors
+
+		/// <summary>
+		/// Initialize a new instance of the <see cref="SingleObjectResolverBase{TResolver, TResolved}"/> class.
+		/// </summary>
+		/// <remarks>By default <c>CanBeNull</c> is false, so <c>Value</c> has to be initialized before being read,
+		/// otherwise an exception will be thrown when reading it.</remarks>
 		protected SingleObjectResolverBase()
 			: this(false)
 		{ }
 
+		/// <summary>
+		/// Initialize a new instance of the <see cref="SingleObjectResolverBase{TResolver, TResolved}"/> class with an instance of the resolved object.
+		/// </summary>
+		/// <param name="value">An instance of the resolved object.</param>
+		/// <remarks>By default <c>CanBeNull</c> is false, so <c>value</c> has to be non-null, or <c>Value</c> has to be
+		/// initialized before being accessed, otherwise an exception will be thrown when reading it.</remarks>
 		protected SingleObjectResolverBase(TResolved value)
 			: this(false)
 		{
 			_resolved = value;
 		}
 
+		/// <summary>
+		/// Initialize a new instance of the <see cref="SingleObjectResolverBase{TResolver, TResolved}"/> class with a value indicating whether the resolved object instance can be null.
+		/// </summary>
+		/// <param name="canBeNull">A value indicating whether the resolved object instance can be null.</param>
+		/// <remarks>If <c>CanBeNull</c> is false, <c>Value</c> has to be initialized before being read,
+		/// otherwise an exception will be thrown when reading it.</remarks>
 		protected SingleObjectResolverBase(bool canBeNull)
 		{
 			_canBeNull = canBeNull;
 		}
 
+		/// <summary>
+		/// Initialize a new instance of the <see cref="SingleObjectResolverBase{TResolver, TResolved}"/> class with an instance of the resolved object,
+		/// and a value indicating whether that instance can be null.
+		/// </summary>
+		/// <param name="value">An instance of the resolved object.</param>
+		/// <param name="canBeNull">A value indicating whether the resolved object instance can be null.</param>
+		/// <remarks>If <c>CanBeNull</c> is false, <c>value</c> has to be non-null, or <c>Value</c> has to be initialized before being read,
+		/// otherwise an exception will be thrown when reading it.</remarks>
 		protected SingleObjectResolverBase(TResolved value, bool canBeNull)
 		{
 			_resolved = value;
 			_canBeNull = canBeNull;
 		}
 
+		#endregion
+
 		/// <summary>
-		/// Gets/sets the value of the object
+		/// Gets a value indicating whether the resolved object instance can be null.
 		/// </summary>
+		public bool CanBeNull
+		{
+			get { return _canBeNull; }
+		}
+
+		/// <summary>
+		/// Gets a value indicating whether the resolved object instance is null.
+		/// </summary>
+		public bool HasValue
+		{
+			get { return _resolved != null; }
+		}
+
+		/// <summary>
+		/// Gets or sets the resolved object instance.
+		/// </summary>
+		/// <remarks></remarks>
+		/// <exception cref="ArgumentNullException">value is set to null, but cannot be null (<c>CanBeNull</c> is <c>false</c>).</exception>
+		/// <exception cref="InvalidOperationException">value is read and is null, but cannot be null (<c>CanBeNull</c> is <c>false</c>).</exception>
 		protected TResolved Value
 		{
 			get
 			{
+				if (!_canBeNull && _resolved == null)
+					throw new InvalidOperationException("");
 				return _resolved;
 			}