AdaptiveAuthentication classes are missing the camelCasing Attribute

source/dotnet/Library/AdaptiveCards/AdaptiveAuthCardButton.cs

@@ -1,13 +1,15 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
 using System.Xml.Serialization;
 
 namespace AdaptiveCards
 {
     /// <summary>
     /// Class for AuthCardButton
     /// </summary>
+    [JsonObject(NamingStrategyType = typeof(CamelCaseNamingStrategy))]
     public class AdaptiveAuthCardButton
     {
         /// <summary>

source/dotnet/Library/AdaptiveCards/AdaptiveAuthentication.cs

@@ -1,29 +1,32 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
 using System.Collections.Generic;
+using System.Net;
 using System.Xml.Serialization;
 
 namespace AdaptiveCards
 {
     /// <summary>
     /// Class to for authentication data.
     /// </summary>
+    [JsonObject(NamingStrategyType = typeof(CamelCaseNamingStrategy))]
     public class AdaptiveAuthentication
     {
         /// <summary>
         ///     Text that can be displayed to the end user when prompting them to authenticate.
         /// </summary>
         [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         [XmlAttribute]
-        public string Text { get; set; }
+        public string Text { get; set; } = "Please sign in";
 
         /// <summary>
         ///     The identifier for registered OAuth connection setting information.
         /// </summary>
         [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         [XmlAttribute]
-        public string ConnectionName { get; set; }
+        public string ConnectionName { get; set; } = "Default";
 
         /// <summary>
         ///     Provides information required to enable on-behalf-of single sign-on user authentication.

source/dotnet/Library/AdaptiveCards/AdaptiveTokenExchangeResource.cs

@@ -1,13 +1,15 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
 using System.Xml.Serialization;
 
 namespace AdaptiveCards
 {
     /// <summary>
     /// Class for TokenExchangeResource
     /// </summary>
+    [JsonObject(NamingStrategyType = typeof(CamelCaseNamingStrategy))]
     public class AdaptiveTokenExchangeResource
     {
         /// <summary>

source/dotnet/Library/AdaptiveCards/ParseContext.cs

@@ -118,14 +118,10 @@ public void PopElement()
                 // add an entry for this element if it's fallback (we'll add one when we parse it for non-fallback)
                 if (!isFallback)
                 {
-                    try
-                    {
-                        elementIds[elementID].Add(nearestFallbackID);
-                    }
-                    catch (KeyNotFoundException)
-                    {
+                    if (!elementIds.TryGetValue(elementID, out var list))
                         elementIds[elementID] = new List<AdaptiveInternalID>() { nearestFallbackID };
-                    }
+                    else 
+                        list.Add(nearestFallbackID);
                 }
             }
             idStack.Pop();