chore: resolve a large number of warnings in csharp codebase (#952)

Removing a host of unused `Using` statements, replacing verbose variable
typings with the `var` keyword, using more expressive syntax for certain
patterns, and resolving a couple of "potential null access" problems.

Author: RomainMuller

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Api/Response/GetResponse.cs

@@ -1,5 +1,4 @@
 using Newtonsoft.Json;
-using System;
 
 namespace Amazon.JSII.JsonModel.Api.Response
 {

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Api/Response/NamingResponse.cs

@@ -1,5 +1,4 @@
-using Amazon.JSII.JsonModel.Converters;
-using Newtonsoft.Json;
+using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
 

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Converters/TypeConverter.cs

@@ -1,6 +1,5 @@
 using Amazon.JSII.JsonModel.Spec;
 using Newtonsoft.Json;
-using Newtonsoft.Json.Linq;
 using System;
 
 namespace Amazon.JSII.JsonModel.Converters

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Converters/TypeDictionaryConverter.cs

@@ -1,27 +1,24 @@
-using Amazon.JSII.JsonModel.Spec;
-using Newtonsoft.Json;
+using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using System;
-using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 
 namespace Amazon.JSII.JsonModel.Converters
 {
-    class TypeDictionaryConverter : JsonConverter
+    internal sealed class TypeDictionaryConverter : JsonConverter
     {
         public override bool CanRead => true;
 
         public override bool CanWrite => false;
 
-        public override bool CanConvert(System.Type objectType)
+        public override bool CanConvert(Type objectType)
         {
             throw new NotImplementedException();
         }
 
-        public override object ReadJson(JsonReader reader, System.Type objectType, object existingValue, JsonSerializer serializer)
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            JObject untypedDictionary = JObject.Load(reader);
+            var untypedDictionary = JObject.Load(reader);
 
             return untypedDictionary.Properties().ToDictionary(p => p.Name, p => Util.ConvertToDerivedType(p.Value));
         }

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Converters/Util.cs

@@ -5,7 +5,7 @@
 
 namespace Amazon.JSII.JsonModel.Converters
 {
-    static class Util
+    internal static class Util
     {
         internal static Spec.Type ConvertToDerivedType(JToken token)
         {
@@ -14,27 +14,18 @@ internal static Spec.Type ConvertToDerivedType(JToken token)
                 throw new ArgumentException($"Unexpected token type: {token.Type}", nameof(token));
             }
 
-            if (token["kind"] is JToken kindToken)
-            {
-                TypeKind kind = kindToken.ToObject<TypeKind>();
-
-                switch (kind)
-                {
-                    case TypeKind.Enum:
-                        return token.ToObject<EnumType>();
-
-                    case TypeKind.Class:
-                        return token.ToObject<ClassType>();
-
-                    case TypeKind.Interface:
-                        return token.ToObject<InterfaceType>();
+            if (!(token["kind"] is {} kindToken))
+                throw new ArgumentException($"Unexpected child token: '{token["kind"]}'", nameof(token));
+            
+            var kind = kindToken.ToObject<TypeKind>();
 
-                    default:
-                        throw new ArgumentException($"Unknown kind {kind} on type {token.ToString(Formatting.Indented)}", nameof(token));
-                }
-            }
-
-            throw new ArgumentException($"Unexpected child token: '{token["kind"]}'", nameof(token));
+            return kind switch
+            {
+                TypeKind.Enum => (Spec.Type) token.ToObject<EnumType>(),
+                TypeKind.Class => token.ToObject<ClassType>(),
+                TypeKind.Interface => token.ToObject<InterfaceType>(),
+                _ => throw new ArgumentException($"Unknown kind {kind} on type {token.ToString(Formatting.Indented)}", nameof(token))
+            };
         }
     }
 }

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/JsonDictionaryBase.cs

@@ -3,9 +3,9 @@
 
 namespace Amazon.JSII.JsonModel
 {
-    public abstract class JsonDictionaryBase<TKey, TValue> : IEnumerable, IEnumerable<KeyValuePair<TKey, TValue>>, IDictionary<TKey, TValue>
+    public abstract class JsonDictionaryBase<TKey, TValue> : IDictionary<TKey, TValue>
     {
-        readonly IDictionary<TKey, TValue> _members = new Dictionary<TKey, TValue>();
+        private readonly IDictionary<TKey, TValue> _members = new Dictionary<TKey, TValue>();
 
         #region IDictionary implementation
 

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Spec/ClassType.cs

@@ -1,5 +1,4 @@
 using Newtonsoft.Json;
-using System;
 
 namespace Amazon.JSII.JsonModel.Spec
 {

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Spec/DependencyRoot.cs

@@ -1,5 +1,4 @@
 using Newtonsoft.Json;
-using System;
 using System.Collections.Generic;
 
 namespace Amazon.JSII.JsonModel.Spec

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Spec/InterfaceType.cs

@@ -1,5 +1,4 @@
 using Newtonsoft.Json;
-using System;
 
 namespace Amazon.JSII.JsonModel.Spec
 {

packages/jsii-dotnet-jsonmodel/src/Amazon.JSII.JsonModel/Spec/Method.cs

@@ -1,5 +1,4 @@
 using Newtonsoft.Json;
-using System;
 
 namespace Amazon.JSII.JsonModel.Spec
 {