Fixing a few issues in ThemeManager (#2992)

* Just a few code style and documentation changes

* We always apply the new theme and accent even if old ones are not found

* If style detection fails on window try on application

* Look at merged dictionaries the way wpf does (in reverse order)

* Using null conditional operator and adding missing documentation

* Using string interpolation

* Using nameof instead of hard coded strings

* Using OrdinalIgnoreCase instead of InvariantCultureIgnoreCase

* Removing empty parameter documentation

* Adding missing documentation

* Fixing documentation text

* Removing "metro" to make porting/sharing of class easier

* Making ReSharper happy

Author: batzen

src/MahApps.Metro/MahApps.Metro.Shared/ThemeManager/Accent.cs

@@ -1,42 +1,44 @@
-using System;
-using System.Diagnostics;
-using System.Windows;
-
+// ReSharper disable once CheckNamespace
 namespace MahApps.Metro
 {
+    using System;
+    using System.Diagnostics;
+    using System.Windows;
+
     /// <summary>
-    /// An object that represents the foreground color for a Metro <see cref="AppTheme"/>.
+    /// An object that represents the foreground color for a <see cref="AppTheme"/>.
     /// </summary>
     [DebuggerDisplay("accent={Name}, res={Resources.Source}")]
     public class Accent
     {
         /// <summary>
         /// The ResourceDictionary that represents this Accent.
         /// </summary>
-        public ResourceDictionary Resources;
+        public ResourceDictionary Resources { get; set; }
+
         /// <summary>
         /// Gets/sets the name of the Accent.
         /// </summary>
         public string Name { get; set; }
 
         /// <summary>
-        /// Initializes a new instance of the MahApps.Metro.Accent class.
+        /// Initializes a new instance of the Accent class.
         /// </summary>
         public Accent()
         { }
 
         /// <summary>
-        /// Initializes a new instance of the MahApps.Metro.Accent class.
+        /// Initializes a new instance of the Accent class.
         /// </summary>
         /// <param name="name">The name of the new Accent.</param>
         /// <param name="resourceAddress">The URI of the accent ResourceDictionary.</param>
         public Accent(string name, Uri resourceAddress)
         {
-            if (name == null) throw new ArgumentException("name");
-            if (resourceAddress == null) throw new ArgumentNullException("resourceAddress");
+            if (name == null) throw new ArgumentNullException(nameof(name));
+            if (resourceAddress == null) throw new ArgumentNullException(nameof(resourceAddress));
 
-            Name = name;
-            Resources = new ResourceDictionary {Source = resourceAddress};
+            this.Name = name;
+            this.Resources = new ResourceDictionary {Source = resourceAddress};
         }
     }
 }

src/MahApps.Metro/MahApps.Metro.Shared/ThemeManager/AppTheme.cs

@@ -1,9 +1,10 @@
-using System;
-using System.Diagnostics;
-using System.Windows;
-
+// ReSharper disable once CheckNamespace
 namespace MahApps.Metro
 {
+    using System;
+    using System.Diagnostics;
+    using System.Windows;
+
     internal class AppName
     {
         public const string MahApps = "MahApps.Metro";
@@ -18,17 +19,22 @@ public class AppTheme
         /// <summary>
         /// The ResourceDictionary that represents this application theme.
         /// </summary>
-        public ResourceDictionary Resources {get; private set;}
+        public ResourceDictionary Resources {get; }
 
         /// <summary>
         /// Gets the name of the application theme.
         /// </summary>
-        public string Name { get; private set; }
+        public string Name { get; }
 
+        /// <summary>
+        /// Initializes a new instance of the AppTheme class.
+        /// </summary>
+        /// <param name="name">The name of the new AppTheme.</param>
+        /// <param name="resourceAddress">The URI of the accent ResourceDictionary.</param>
         public AppTheme(string name, Uri resourceAddress)
         {
-            if (name == null) throw new ArgumentException("name");
-            if (resourceAddress == null) throw new ArgumentNullException("resourceAddress");
+            if (name == null) throw new ArgumentNullException(nameof(name));
+            if (resourceAddress == null) throw new ArgumentNullException(nameof(resourceAddress));
 
             this.Name = name;
             this.Resources = new ResourceDictionary {Source = resourceAddress};