diff --git a/samples/csharp_dotnetcore/03.welcome-user/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/03.welcome-user/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/03.welcome-user/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/03.welcome-user/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/05.multi-turn-prompt/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/05.multi-turn-prompt/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/05.multi-turn-prompt/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/05.multi-turn-prompt/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/06.using-cards/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/06.using-cards/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/06.using-cards/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/06.using-cards/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/07.using-adaptive-cards/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/07.using-adaptive-cards/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/07.using-adaptive-cards/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/07.using-adaptive-cards/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/08.suggested-actions/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/08.suggested-actions/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/08.suggested-actions/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/08.suggested-actions/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/11.qnamaker/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/11.qnamaker/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/11.qnamaker/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/11.qnamaker/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/13.core-bot/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/13.core-bot/AdapterWithErrorHandler.cs
index a47fa1443f..c845fd7ec4 100644
--- a/samples/csharp_dotnetcore/13.core-bot/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/13.core-bot/AdapterWithErrorHandler.cs
@@ -14,7 +14,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/14.nlp-with-dispatch/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/14.nlp-with-dispatch/AdapterWithErrorHandler.cs
index 7229989d4c..8404a18a2a 100644
--- a/samples/csharp_dotnetcore/14.nlp-with-dispatch/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/14.nlp-with-dispatch/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/15.handling-attachments/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/15.handling-attachments/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/15.handling-attachments/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/15.handling-attachments/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/16.proactive-messages/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/16.proactive-messages/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/16.proactive-messages/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/16.proactive-messages/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/17.multilingual-bot/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/17.multilingual-bot/AdapterWithErrorHandler.cs
index c571675a57..6691869cca 100644
--- a/samples/csharp_dotnetcore/17.multilingual-bot/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/17.multilingual-bot/AdapterWithErrorHandler.cs
@@ -16,7 +16,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, TranslationMiddleware translationMiddleware, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, TranslationMiddleware translationMiddleware, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             if (translationMiddleware == null)
diff --git a/samples/csharp_dotnetcore/18.bot-authentication/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/18.bot-authentication/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/18.bot-authentication/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/18.bot-authentication/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/19.custom-dialogs/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/19.custom-dialogs/AdapterWithErrorHandler.cs
index fb0743826e..e7d6d04fe8 100644
--- a/samples/csharp_dotnetcore/19.custom-dialogs/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/19.custom-dialogs/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         { 
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/21.corebot-app-insights/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/21.corebot-app-insights/AdapterWithErrorHandler.cs
index 15c3bd51f4..a49908956c 100644
--- a/samples/csharp_dotnetcore/21.corebot-app-insights/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/21.corebot-app-insights/AdapterWithErrorHandler.cs
@@ -19,7 +19,7 @@ public class AdapterWithErrorHandler : CloudAdapter
         //Create field for telemetry client. Add IBotTelemetryClient parameter to AdapterWithErrorHandler
         private IBotTelemetryClient _adapterBotTelemetryClient;
 
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, TelemetryInitializerMiddleware telemetryInitializerMiddleware, IBotTelemetryClient botTelemetryClient, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, TelemetryInitializerMiddleware telemetryInitializerMiddleware, IBotTelemetryClient botTelemetryClient, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             Use(telemetryInitializerMiddleware);
diff --git a/samples/csharp_dotnetcore/23.facebook-events/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/23.facebook-events/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/23.facebook-events/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/23.facebook-events/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/24.bot-authentication-msgraph/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/24.bot-authentication-msgraph/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/24.bot-authentication-msgraph/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/24.bot-authentication-msgraph/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/42.scaleout/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/42.scaleout/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/42.scaleout/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/42.scaleout/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/43.complex-dialog/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/43.complex-dialog/AdapterWithErrorHandler.cs
index c5402753ef..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/43.complex-dialog/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/43.complex-dialog/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/44.prompt-users-for-input/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/44.prompt-users-for-input/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/44.prompt-users-for-input/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/44.prompt-users-for-input/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/45.state-management/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/45.state-management/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/45.state-management/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/45.state-management/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/46.teams-auth/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/46.teams-auth/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/46.teams-auth/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/46.teams-auth/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/49.qnamaker-all-features/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/49.qnamaker-all-features/AdapterWithErrorHandler.cs
index b8c77f87c2..9f7c3c02e6 100644
--- a/samples/csharp_dotnetcore/49.qnamaker-all-features/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/49.qnamaker-all-features/AdapterWithErrorHandler.cs
@@ -13,7 +13,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/52.teams-messaging-extensions-search-auth-config/AdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/52.teams-messaging-extensions-search-auth-config/AdapterWithErrorHandler.cs
index 972a3c4b76..78fb123159 100644
--- a/samples/csharp_dotnetcore/52.teams-messaging-extensions-search-auth-config/AdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/52.teams-messaging-extensions-search-auth-config/AdapterWithErrorHandler.cs
@@ -15,7 +15,7 @@ namespace Microsoft.BotBuilderSamples
 {
     public class AdapterWithErrorHandler : CloudAdapter
     {
-        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = null)
+        public AdapterWithErrorHandler(IConfiguration configuration, IHttpClientFactory httpClientFactory, ILogger<IBotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, httpClientFactory, logger)
         {
             OnTurnError = async (turnContext, exception) =>
diff --git a/samples/csharp_dotnetcore/81.skills-skilldialog/DialogSkillBot/SkillAdapterWithErrorHandler.cs b/samples/csharp_dotnetcore/81.skills-skilldialog/DialogSkillBot/SkillAdapterWithErrorHandler.cs
index dc1d2f043e..1f04e177e6 100644
--- a/samples/csharp_dotnetcore/81.skills-skilldialog/DialogSkillBot/SkillAdapterWithErrorHandler.cs
+++ b/samples/csharp_dotnetcore/81.skills-skilldialog/DialogSkillBot/SkillAdapterWithErrorHandler.cs
@@ -18,7 +18,7 @@ public class SkillAdapterWithErrorHandler : BotFrameworkHttpAdapter
         private readonly ConversationState _conversationState;
         private readonly ILogger _logger;
 
-        public SkillAdapterWithErrorHandler(IConfiguration configuration, ICredentialProvider credentialProvider, AuthenticationConfiguration authConfig, ILogger<BotFrameworkHttpAdapter> logger, ConversationState conversationState)
+        public SkillAdapterWithErrorHandler(IConfiguration configuration, ICredentialProvider credentialProvider, AuthenticationConfiguration authConfig, ILogger<BotFrameworkHttpAdapter> logger, ConversationState conversationState = default)
             : base(configuration, credentialProvider, authConfig, logger: logger)
         {
             _conversationState = conversationState ?? throw new ArgumentNullException(nameof(conversationState));