NSwag cannot handle nullable types in Dto

Question

In my ASP.Net Core project I use NSwag to generate clients. And everything works fine. The only problem I have is, that my nullable types are ignored in the response when they are null.

I have the following classes:

class ClassA {
    public int Test { get; set; }  
}

class ClassB {
    public string? Name { get; set; }
    public ClassA? SomeProperty { get; set; }
}

When I generate the client, both properties will be created with the following Attribute:

[Newtonsoft.Json.JsonProperty("someProperty", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]

I tried the following things that do not work:

• Set the NullValueHandling = Newtonsoft.Json.NullValueHandling.Include in my class, but it gets overridden
• Implement a partial class next to the generated one and fix the NullValueHandling, as described here (https://github.com/RicoSuter/NSwag/issues/1129), but it still gets ignored
• Trying multiple settings that I can set in the "openApiToCSharpClient" Json Object

EDIT: ClassA should be nullable too

Answer 1

There is no direct option to use this feature with NSwag. However, it is possible to customize the NSwag configuration and add this setting manually.

This example will exclude properties that are null from the JSON output using the IgnoreNullValues ​​property.

 var document = await OpenApiDocument.FromUrlAsync("https://example.com/swagger/v1/swagger.json");


var jsonSerializerSettings = document.ToJsonSerializerSettings();


jsonSerializerSettings.NullValueHandling = NullValueHandling.Ignore;


document.SerializerSettings = jsonSerializerSettings;


var codeGeneratorSettings = new CSharpClientGeneratorSettings
{
    ClassName = "MyApiClient",
    Namespace = "MyNamespace",
};
var clientCode = new CSharpClientGenerator(document, codeGeneratorSettings)
    .GenerateFile();

Answer 2

modify the property to :

[Newtonsoft.Json.JsonProperty("someProperty", Required = Newtonsoft.Json.Required.AllowNull, NullValueHandling = Newtonsoft.Json.NullValueHandling.Include)]

Now the result: