Be draconian about using readonly where appropriate

Stylet/ConductorAllActive.cs

@@ -19,7 +19,7 @@ namespace Stylet
             /// </summary>
             public class AllActive : ConductorBase<T>
             {
-                private BindableCollection<T> items = new BindableCollection<T>();
+                private readonly BindableCollection<T> items = new BindableCollection<T>();
 
                 /// <summary>
                 /// All items associated with this conductor

Stylet/ConductorNavigating.cs

@@ -13,7 +13,7 @@ namespace Stylet
         public class StackNavigation : ConductorBaseWithActiveItem<T>
         {
             // We need to remove arbitrary items, so no Stack<T> here!
-            private List<T> history = new List<T>();
+            private readonly List<T> history = new List<T>();
 
             /// <summary>
             /// Activate the given item. This deactivates the previous item, and pushes it onto the history stack

Stylet/ConductorOneActive.cs

@@ -15,7 +15,7 @@ namespace Stylet
             /// </summary>
             public class OneActive : ConductorBaseWithActiveItem<T>
             {
-                private BindableCollection<T> items = new BindableCollection<T>();
+                private readonly BindableCollection<T> items = new BindableCollection<T>();
 
                 /// <summary>
                 /// Items owned by this Conductor, one of which is active

Stylet/EventAggregator.cs

@@ -123,7 +123,7 @@ namespace Stylet
         {
             private readonly WeakReference target;
             private readonly List<HandlerInvoker> invokers = new List<HandlerInvoker>();
-            private HashSet<string> channels = new HashSet<string>();
+            private readonly HashSet<string> channels = new HashSet<string>();
 
             public Handler(object handler, string[] channels)
             {

Stylet/ValidatingModelBase.cs

@@ -29,7 +29,7 @@ namespace Stylet
         /// <summary>
         /// IModelValidator to use to validate properties. You're expected to write your own, using your favourite validation library
         /// </summary>
-        protected virtual IModelValidator validator
+        protected virtual IModelValidator Validator
         {
             get { return this._validator; }
             set
@@ -98,7 +98,7 @@ namespace Stylet
         /// <remarks>If you override this, you MUST fire ErrorsChanged as appropriate, and call ValidationStateChanged</remarks>
         protected virtual async Task<bool> ValidateAsync()
         {
-            if (this.validator == null)
+            if (this.Validator == null)
                 throw new InvalidOperationException("Can't run validation if a validator hasn't been set");
 
             bool anyChanged = false;
@@ -107,7 +107,7 @@ namespace Stylet
             // However this means that the stuff after the await can be run in parallel on multiple threads
             // Therefore, we need the lock
             // However, we can't raise PropertyChanged events from within the lock, otherwise deadlock
-            var results = await this.validator.ValidateAllPropertiesAsync().ConfigureAwait(false);
+            var results = await this.Validator.ValidateAllPropertiesAsync().ConfigureAwait(false);
             var changedProperties = new List<string>();
             await this.propertyErrorsLock.WaitAsync().ConfigureAwait(false);
             {
@@ -185,12 +185,12 @@ namespace Stylet
         /// <remarks>If you override this, you MUST fire ErrorsChange and call OnValidationStateChanged() if appropriate</remarks>
         protected virtual async Task<bool> ValidatePropertyAsync([CallerMemberName] string propertyName = null)
         {
-            if (this.validator == null)
+            if (this.Validator == null)
                 throw new InvalidOperationException("Can't run validation if a validator hasn't been set");
 
             // To allow synchronous calling of this method, we need to resume on the ThreadPool.
             // Therefore, we might resume on any thread, hence the need for a lock
-            var newErrors = await this.validator.ValidatePropertyAsync(propertyName).ConfigureAwait(false);
+            var newErrors = await this.Validator.ValidatePropertyAsync(propertyName).ConfigureAwait(false);
             bool propertyErrorsChanged = false;
 
             await this.propertyErrorsLock.WaitAsync().ConfigureAwait(false);
@@ -222,7 +222,7 @@ namespace Stylet
 
             // Save ourselves a little bit of work every time HasErrors is fired as the result of 
             // the validation results changing.
-            if (this.validator != null && this.AutoValidate && propertyName != "HasErrors")
+            if (this.Validator != null && this.AutoValidate && propertyName != "HasErrors")
                 await this.ValidatePropertyAsync(propertyName);
         }
 

Stylet/Xaml/ApplicationLoader.cs

@@ -8,7 +8,7 @@ namespace Stylet.Xaml
     /// </summary>
     public class ApplicationLoader : ResourceDictionary
     {
-        private ResourceDictionary styletResourceDictionary;
+        private readonly ResourceDictionary styletResourceDictionary;
 
         /// <summary>
         /// Create a new ApplicationLoader instance

Stylet/Xaml/CommandAction.cs

@@ -41,8 +41,8 @@ namespace Stylet.Xaml
 
         private object target;
 
-        private ActionUnavailableBehaviour targetNullBehaviour;
-        private ActionUnavailableBehaviour actionNonExistentBehaviour;
+        private readonly ActionUnavailableBehaviour targetNullBehaviour;
+        private readonly ActionUnavailableBehaviour actionNonExistentBehaviour;
 
         /// <summary>
         /// Create a new ActionCommand 

Stylet/Xaml/EventAction.cs

@@ -35,8 +35,8 @@ namespace Stylet.Xaml
 
         private object target;
 
-        private ActionUnavailableBehaviour targetNullBehaviour;
-        private ActionUnavailableBehaviour actionNonExistentBehaviour;
+        private readonly ActionUnavailableBehaviour targetNullBehaviour;
+        private readonly ActionUnavailableBehaviour actionNonExistentBehaviour;
 
         /// <summary>
         /// Create a new EventAction

Stylet/Xaml/IconToBitmapSourceConverter.cs

@@ -15,7 +15,7 @@ namespace Stylet.Xaml
         /// <summary>
         /// Singleton instance of this converter. Usage e.g. Converter="{x:Static s:IconToBitmapSourceConverter.Instance}"
         /// </summary>
-        public static IconToBitmapSourceConverter Instance = new IconToBitmapSourceConverter();
+        public static readonly IconToBitmapSourceConverter Instance = new IconToBitmapSourceConverter();
 
         /// <summary>
         /// Converts a value

StyletUnitTests/ScreenTests.cs

@@ -17,10 +17,10 @@ namespace StyletUnitTests
     {
         private class MyScreen : Screen
         {
-            public IModelValidator Validator
+            public new IModelValidator Validator
             {
-                get { return base.validator; }
-                set { base.validator = value; }
+                get { return base.Validator; }
+                set { base.Validator = value; }
             }
 
             public MyScreen() { }

StyletUnitTests/ValidatingModelBaseTests.cs

@@ -31,10 +31,10 @@ namespace StyletUnitTests
                 set { base.AutoValidate = value; }
             }
 
-            public IModelValidator Validator
+            public new IModelValidator Validator
             {
-                get { return this.validator; }
-                set { this.validator = value; }
+                get { return base.Validator; }
+                set { base.Validator = value; }
             }
 
             public new bool Validate()