diff --git a/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache b/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache
index 33c8f991218..5c42d2e4fe3 100644
--- a/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/ClientUtils.mustache
@@ -114,6 +114,14 @@ namespace {{packageName}}.Client
                 // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
                 // For example: 2009-06-15T13:45:30.0000000
                 return dateTimeOffset.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
+{{#net60OrLater}}
+            if (obj is DateOnly dateOnly)
+                // Return a formatted date string - Can be customized with Configuration.DateTimeFormat
+                // Defaults to an ISO 8601, using the known as a Round-trip date/time pattern ("o")
+                // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
+                // For example: 2009-06-15
+                return dateOnly.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
+{{/net60OrLater}}
             if (obj is bool boolean)
                 return boolean ? "true" : "false";
             if (obj is ICollection collection) {
diff --git a/samples/client/echo_api/csharp-restsharp/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/echo_api/csharp-restsharp/src/Org.OpenAPITools/Client/ClientUtils.cs
index 024e2d7b339..116c891b464 100644
--- a/samples/client/echo_api/csharp-restsharp/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/echo_api/csharp-restsharp/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -101,6 +101,12 @@ namespace Org.OpenAPITools.Client
                 // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
                 // For example: 2009-06-15T13:45:30.0000000
                 return dateTimeOffset.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
+            if (obj is DateOnly dateOnly)
+                // Return a formatted date string - Can be customized with Configuration.DateTimeFormat
+                // Defaults to an ISO 8601, using the known as a Round-trip date/time pattern ("o")
+                // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
+                // For example: 2009-06-15
+                return dateOnly.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
             if (obj is bool boolean)
                 return boolean ? "true" : "false";
             if (obj is ICollection collection) {
diff --git a/samples/client/petstore/csharp/restsharp/net6/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net6/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
index 6f180ece250..5ebe54e2046 100644
--- a/samples/client/petstore/csharp/restsharp/net6/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net6/ParameterMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -100,6 +100,12 @@ namespace Org.OpenAPITools.Client
                 // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
                 // For example: 2009-06-15T13:45:30.0000000
                 return dateTimeOffset.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
+            if (obj is DateOnly dateOnly)
+                // Return a formatted date string - Can be customized with Configuration.DateTimeFormat
+                // Defaults to an ISO 8601, using the known as a Round-trip date/time pattern ("o")
+                // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
+                // For example: 2009-06-15
+                return dateOnly.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
             if (obj is bool boolean)
                 return boolean ? "true" : "false";
             if (obj is ICollection collection) {
diff --git a/samples/client/petstore/csharp/restsharp/net7/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net7/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
index bd0ca59f211..a3765e00229 100644
--- a/samples/client/petstore/csharp/restsharp/net7/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net7/EnumMappings/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -116,6 +116,12 @@ namespace Org.OpenAPITools.Client
                 // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
                 // For example: 2009-06-15T13:45:30.0000000
                 return dateTimeOffset.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
+            if (obj is DateOnly dateOnly)
+                // Return a formatted date string - Can be customized with Configuration.DateTimeFormat
+                // Defaults to an ISO 8601, using the known as a Round-trip date/time pattern ("o")
+                // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
+                // For example: 2009-06-15
+                return dateOnly.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
             if (obj is bool boolean)
                 return boolean ? "true" : "false";
             if (obj is ICollection collection) {
diff --git a/samples/client/petstore/csharp/restsharp/net7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index bd0ca59f211..a3765e00229 100644
--- a/samples/client/petstore/csharp/restsharp/net7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -116,6 +116,12 @@ namespace Org.OpenAPITools.Client
                 // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
                 // For example: 2009-06-15T13:45:30.0000000
                 return dateTimeOffset.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
+            if (obj is DateOnly dateOnly)
+                // Return a formatted date string - Can be customized with Configuration.DateTimeFormat
+                // Defaults to an ISO 8601, using the known as a Round-trip date/time pattern ("o")
+                // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
+                // For example: 2009-06-15
+                return dateOnly.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
             if (obj is bool boolean)
                 return boolean ? "true" : "false";
             if (obj is ICollection collection) {
diff --git a/samples/client/petstore/csharp/restsharp/net7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/restsharp/net7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index e61321cb82c..02d02e36292 100644
--- a/samples/client/petstore/csharp/restsharp/net7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/restsharp/net7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -100,6 +100,12 @@ namespace Org.OpenAPITools.Client
                 // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
                 // For example: 2009-06-15T13:45:30.0000000
                 return dateTimeOffset.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
+            if (obj is DateOnly dateOnly)
+                // Return a formatted date string - Can be customized with Configuration.DateTimeFormat
+                // Defaults to an ISO 8601, using the known as a Round-trip date/time pattern ("o")
+                // https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx#Anchor_8
+                // For example: 2009-06-15
+                return dateOnly.ToString((configuration ?? GlobalConfiguration.Instance).DateTimeFormat);
             if (obj is bool boolean)
                 return boolean ? "true" : "false";
             if (obj is ICollection collection) {