创建与您的JSON相对应的类:

Create a class that corresponds to your JSON:

public class Test
{
    public string value{get; set;}
    public int ID {get; set;}
}

然后更改您的Api动作:

And then change your Api-action:

// POST api/myfiles
public void Post([FromBody]Test value)
{

}

如果您不想这样做，只需更改POST-body:

If you don't want to do that, just change the POST-body:

"somevalue"

编辑:将ID添加到POST有效负载中. 现在，您的JSON应该如下所示:

EDIT: Added ID to the POST-payload. Now your JSON should look like this:

{"value": "someval",
"ID": 1}