将 JSON 字符串 integer 反序列化为 ASP.NET 内核中的枚举

Question

I'm creating an ASP.NET Core API and my users have a role, like so

class User
{
    public Guid Id {get; set;}

    public string Email {get; set;}

    public Role Role {get; set;}
}

enum Role : byte
{
    User = 0,
    Administrator = 1
}

The problem now is, that my user CreateOrUpdate endpoint is getting this JSON data

{
    "id": "2abe50d6-4c81-4ace-ad95-c8182d4384a3",
    "email": "someEmail@example.org",
    "role": "0"
}

Here's the problematic endpoint declaration

public User CreateOrUpdate([FromBody] User user)
{
    // ...
}

And it fails to deserialize this, and as such returns HTTP 400 Bad Request . But, if I remove the quotation marks around the 0 of the role property, it works like a charm.

So, how do I get ASP.NET Core to deserialize the "0" to a 0 and as such to the enum variant User ?

Answer 1

You have to write your own converter. Depending, if you're using either Newtonsoft or Microsoft.Json.Text the implementation are more or less the same, but you have to take care to use the classes and properties out of the right namespace and do not mix them.

Depending on your usage you can take a look into the original code of the StringEnumConverter either at Microsoft or Newtonsoft and write your own based on that.

In your class you can then apply this converter by using the corresponding attribute to the specific attribute.

Answer 2

From How to customize property names and values with System.Text.Json - Enum as string .

By default, System.Text.Json convert enum from integer, but in you case "0" is a string. You need specify a converter to convert enum from string like:

public void ConfigureServices(IServiceCollection services)
{

    services.AddControllers().AddJsonOptions(o =>
    {
        o.JsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
        o.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
    });
}