[csharp] Output DateOnly paramater in the correct default format (#19728) (#19729)

* Output DateOnly in the correct default format

* Only add conditional if we are net60 or later

* Update samples

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) {

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) {

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) {

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) {

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) {

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) {