Minor fixes

src/Stripe.net/Infrastructure/Middleware/RequestStringBuilder.cs

@@ -214,13 +214,10 @@ private static List<Parameter> FlattenParamsList(List<object> list, string keyPr
             }
             else
             {
-                var listEnumerator = list.GetEnumerator();
-
-                for (int i = 0; listEnumerator.MoveNext() == true; i++)
+                foreach (var item in list.Select((value, index) => new { value, index }))
                 {
-                    object value = listEnumerator.Current;
-                    string newPrefix = $"{keyPrefix}[{i}]";
-                    flatParams.AddRange(FlattenParamsValue(value, newPrefix));
+                    string newPrefix = $"{keyPrefix}[{item.index}]";
+                    flatParams.AddRange(FlattenParamsValue(item.value, newPrefix));
                 }
             }
 

src/Stripe.net/Infrastructure/ParameterBuilder.cs

@@ -54,12 +54,6 @@ public static string ApplyAllParameters<T>(this Service<T> service, BaseOptions
                     }
 
                     requestString = ApplyParameterToUrl(requestString, "expand[]", expandPropertyName);
-
-                    // note: I had no idea you could expand properties beyond the first level (up to 4 before stripe throws an exception).
-                    // something to consider adding to the project.
-                    //
-                    // example:
-                    // requestString = ApplyParameterToUrl(requestString, "expand[]", "data.charge.dispute.charge.dispute.charge.dispute");
                 }
             }
 

src/StripeTests/Infrastructure/ParameterBuilderTest.cs

@@ -354,7 +354,6 @@ public void SetsUrl()
         {
             Assert.NotNull(this.service);
 
-            var testObject = new TestOptions();
             var url = this.service.ApplyAllParameters(null, "base_url", false);
             Assert.Equal("base_url", url);
         }

src/StripeTests/MockHttpClientFixture.cs

@@ -9,9 +9,9 @@ namespace StripeTests
 
     public class MockHttpClientFixture : IDisposable
     {
-        private Mock<HttpClientHandler> mockHandler;
+        private readonly Mock<HttpClientHandler> mockHandler;
 
-        private HttpMessageHandler origHandler;
+        private readonly HttpMessageHandler origHandler;
 
         public MockHttpClientFixture()
         {

src/StripeTests/StripeMockFixture.cs

@@ -14,11 +14,11 @@ public class StripeMockFixture : IDisposable
         /// </remarks>
         private const string MockMinimumVersion = "0.39.0";
 
-        private string origApiBase;
-        private string origFilesBase;
-        private string origApiKey;
+        private readonly string origApiBase;
+        private readonly string origFilesBase;
+        private readonly string origApiKey;
 
-        private string port;
+        private readonly string port;
 
         public StripeMockFixture()
         {