ASP.NET Core API POST parameter is always null

Question

I have read the following:

• Asp.net Core Post parameter is always null
• asp.net webapi 2 post parameter is always null
• web-api POST body object

Answer 1

In my case, I had it setup like @guhyeon suggested, with a model class containing only a string property. Except, it wasn't defined as a property, it was simply

public class PdfInfoRequestDto
{
    public string PdfInBase64;
}

And for some reason, this worked for a .net framework 4.7.2 webapi and I could receive the value I needed from the request body. But when I tried replicating the same in a .net core 3.1 webapi, with the same request, models and everything, the value in PdfInBase64 always arrived in my controller as null. After changing the field to a property:

public string PdfInBase64 { get; set; }

I started correctly getting the value that was being passed in the request body.