asp.net core razor pages: get body of ajax call in controller function

Question

Say i have this ajax to the server:

$.ajax({
                type: 'POST',
                url: "/Jobs/Sprachen/?handler=RandomNumber",
                data: JSON.stringify({ Min: testvariable, Max: "no" }),
                contentType: "application/json",
                dataType: "json",
            }).done(function (data) {
                console.log(data);
            })
            .fail(function (error) {
                //nothing for now
            });

... and I have this function:

public IActionResult OnPostRandomNumber([FromBody]string input)
        {
            // called from ajax (no page reload) 
            return new JsonResult("input: "+input);
        }

Why is there always "null" on my input variable?

I wouldve expected a json.

The function it self fires fine and the result is returned and written to the console, but never with anything on the variable

Answer 1

Asp.Net Core achieve model binding via property's name. Here your parameter can't match to the data you send in ajax. You can create a model contains Max and Min property, then use this model as parameter.

public class Input
    {
        //I'm not sure what's the type of Max property, I use string to test.
        public string? Max { get; set; }
        public string Min { get; set; }
    }

Then in the backend

public IActionResult OnPostRandomNumber([FromBody]Input model)
        {
            // called from ajax (no page reload) 
            return new JsonResult(model);
        }

Now the parameter can receive data successfully