Optimize dictionary usage and improve code readability

Updated MessageBinder.cs:
- Modified SpecialValues dictionary initialization for consistent formatting and alignment.
- Optimized custom converter checks using TryGetValue for better performance and readability.
- Adjusted conditional compilation blocks for enum type checks for improved readability and consistency across platforms.

Updated FrameAdapter.cs:
- Simplified ResumeStateAsync method by using TryGetValue for dictionary lookups, enhancing performance.
- Streamlined CurrentParameter assignment with TryGetValue for efficiency.

src/Caliburn.Micro.Platform/MessageBinder.cs

@@ -34,8 +34,8 @@ public static class MessageBinder
             {
                 ["$eventargs"] = c => c.EventArgs,
 #if XFORMS || MAUI
-            ["$datacontext"] = c => c.Source.BindingContext,
-            ["$bindingcontext"] = c => c.Source.BindingContext,
+                ["$datacontext"] = c => c.Source.BindingContext,
+                ["$bindingcontext"] = c => c.Source.BindingContext,
 #else
                 ["$datacontext"] = c => c.Source.DataContext,
 #endif
@@ -120,9 +120,9 @@ public static object CoerceValue(Type destinationType, object providedValue, obj
                 return providedValue;
             }
 
-            if (CustomConverters.ContainsKey(destinationType))
+            if (CustomConverters.TryGetValue(destinationType, out Func<object, object, object> value))
             {
-                return CustomConverters[destinationType](providedValue, context);
+                return value;
             }
             try
             {
@@ -142,7 +142,8 @@ public static object CoerceValue(Type destinationType, object providedValue, obj
                 }
 #endif
 #if WINDOWS_UWP || XFORMS || MAUI
-    if (destinationType.GetTypeInfo().IsEnum) {
+                if (destinationType.GetTypeInfo().IsEnum)
+                {
 #else
                 if (destinationType.IsEnum)
                 {

src/Caliburn.Micro.Platform/Platforms/uap/FrameAdapter.cs

@@ -368,14 +368,13 @@ public virtual async Task<bool> ResumeStateAsync()
         {
             var container = GetSettingsContainer();
 
-            if (!container.Values.ContainsKey(FrameStateKey))
+            if (!container.Values.TryGetValue(FrameStateKey, out object stateKeyValue))
                 return false;
 
-            var frameState = (string)container.Values[FrameStateKey];
+            var frameState = (string)stateKeyValue;
 
-            CurrentParameter = container.Values.ContainsKey(ParameterKey) ?
-                container.Values[ParameterKey] :
-                null;
+            CurrentParameter = container.Values.TryGetValue(ParameterKey, out object parameterKeyValue) ?
+                parameterKeyValue : null;
 
             if (String.IsNullOrEmpty(frameState))
                 return false;