ASP.NET Core MVC - Model Binding does not work for POST Request when Number Properties are Declared-CodePudding

I have a controller route in ASP.NET Core that accepts application/json data. I was intending to convert some form data on the client-side into JSON as follows:

let formElement = document.getElementById("form-data");
let formData = new FormData(formElement);
let formJson = Object.fromEntries(formData.entries());

console.log("submitting:", formJson)

let response = await request("/mycontroller/addnew", "POST", formJson);

With the server-side route as follows:

[HttpPost]
public IActionResult AddNew([FromBody] MyFormData formData )
{
    // Do Stuff
}

public class MyFormData 
{
    public int Id { get; set; }
    public string Message { get; set; }
}

With the example setup above, I can get the MyFormData model to bind correctly if I submit:

{
    "id": 123,
    "message": "testing testing"
}

However, when I submit the following, formData is null:

{
    "id": "123",
    "message": "testing testing"
}

Given that you cannot specify data types in the HTML form, it'd be a pain to explicitly cast all my properties to their correct types. The documentation below also implies that the server should be able to handle numbers expressed as strings by default:

https://andrewlock.net/model-binding-json-posts-in-asp-net-core/ https://docs.microsoft.com/en-us/aspnet/core/mvc/models/model-binding?view=aspnetcore-6.0

Am I missing anything obvious here or is this expected behaviour?

CodePudding user response：

It looks like the modelbinding is not behaving as you expect it. This can be configured in the startup with:

services.AddMvc().AddJsonOptions(o =>
{o.JsonSerializerOptions.PropertyNamingPolicy = null;
o.JsonSerializerOptions.DictionaryKeyPolicy = null; });

Also, I have solved this issue in my projects with using application/x-www-form-urlencoded as content-type in the post requests in the clientside. You may need to remove the [frombody] tag if you're using this method.

CodePudding user response：

Starting from .NET Core 5, it looks as though you can configure number handling as follows:

services
    .AddControllersWithViews()
    .AddJsonOptions(o => o.JsonSerializerOptions.NumberHandling = JsonNumberHandling.AllowReadingFromString );

https://docs.microsoft.com/en-us/dotnet/api/system.text.json.jsonserializeroptions.numberhandling?view=net-6.0&viewFallbackFrom=netcore-3.1#system-text-json-jsonserializeroptions-numberhandling

For older versions, the application/x-www-form-urlencoded approach is probably the most straightforward.