C＃HttpWebResponse sendin null JSON字符串

Question

This has me really stumped. I have a Web API handler for POST that looks like this:

    [HttpPost]
    public IActionResult Post([FromBody]string jsonString)
    {
        if (jsonString == null)
            return new ObjectResult("Bad JSON");

My caller looks like this (borrowed from How to post JSON to the server? ):

    public async void PostJson(string path, string payload)
    {
        string url = string.Format("{0}{1}", BaseAddress, path); // Not the issue, the URL is good...
        var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
        httpWebRequest.ContentType = "application/json";
        httpWebRequest.Method = "POST";

        using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
        {
            streamWriter.Write(payload);
            streamWriter.Flush();
            streamWriter.Close();
        }

        var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
        using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
        {
            var result = streamReader.ReadToEnd();
            Console.WriteLine(string.Format("Response: {0}", result.ToString()));
            Console.WriteLine("Press any key...");
            Console.ReadKey();
        }

} Here's the problem. When I use POSTMAN to post the JSON string (as supplied in payload), my WebApi gets the correct JSON string. Yet, when I use the code listed above (and many other methods I've tried by researching this) I consistently get a NULL value for jsonString in my web api.

Can anyone shed any light on this?

Answer 1

I found the answer here: ASP.NET Core API POST parameter is always null

I must admit that I hadn't considered this approach when I first ran across it earlier in the day, but to paraphrase Sherlock Holmes, once you have exhausted the other possibilities...

In short, I changed the Content type to text/plain and added a formatter to my web api Startup.cs file (as shown in the other link) and this worked.