How to POST a string HttpContent using HttpClient to an ASP.net Core web API?

Question

User-1758582694 posted

Using C# HttpClient, how to POST a string HttpContent to ASP.net Core web API?

 

On client side, I Post a request using HttpClient class to an ASP.net core web API on server side.

 

I want to send a string ("OK") in the body of the request, and a string argument (numStr=5) in the header, I've read many similar thread but still failed.

 

Here is the Client Method:

 

    public async void SendBodyAsync(Action<string> onRespond)

    {

        try

        {

            string URL = "http://localhost:60039/api/calculator/AddMore";

 

            HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, URL);

            request.Headers.Add("numStr", "5");

 

            request.Content = new StringContent("OK", Encoding.UTF8, "text/plain");   //causes error

 

            HttpResponseMessage response = await mHttpClient.SendAsync(request);

            response.EnsureSuccessStatusCode();

 

            string result = await response.Content.ReadAsStringAsync();

            onRespond(result);

        }

        catch (HttpRequestException ex)

        {

            Debug.LogError(ex);       //Unity3D console Debug

            onRespond(null);

        }

    }

Here is the Server Action:

 

[Route("api/[controller]/[action]")]

[ApiController]

public class CalculatorController : ControllerBase

{

    public string AddMore([FromHeader]string numStr)

    {

        //string bodyStr;

        //get string from Request.Body and set the value to bodyStr

        return (int.Parse(numStr) + 10).ToString();

    }

}

If I remove the line "request.Content = new StringContent("OK", Encoding.UTF8, "text/plain");" from the client method, the respond value is "15" which is correct.

 

But with the request.Content, the client shows an error "An error occurred while sending the request ---> System.Net.WebException: The request requires buffering data to succeed". The server break point is not triggered, so the request was not sent out successfully.

 

I have created another very simple server method using HttpListener, it reads the request.Content as clientContext stream correctly. I think maybe the problem is that request.Content is not equal to Http body, and it's unlikely a buffering issue as the error message says.

 

My questions are, 1. How to send a string in Http body correctly, it's not argument and can be long (like a complete player profile in string format), so it's not proper for header or query or... 2. How can I receive and parse the string in the request body on server side correctly?

 

Thank you so much for reading my post.

Answer 1

User1120430333 posted

<div>Using C# HttpClient, how to POST a string HttpContent to ASP.net Core web API?</div> <div> </div> <div>On client side, I Post a request using HttpClient class to an ASP.net core web API on server side.</div> <div> </div> <div>I want to send a string ("OK") in the body of the request, and a string argument (numStr=5) in the header, I've read many similar thread but still failed.</div> <div> </div> <div>Here is the Client Method:</div> <div> </div> <div>    public async void SendBodyAsync(Action<string> onRespond)</div> <div>    {</div> <div>        try</div> <div>        {</div> <div>            string URL = "http://localhost:60039/api/calculator/AddMore";</div> <div> </div> <div>            HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, URL);</div> <div>            request.Headers.Add("numStr", "5");</div> <div> </div> <div>            request.Content = new StringContent("OK", Encoding.UTF8, "text/plain");   //causes error</div> <div> </div> <div>            HttpResponseMessage response = await mHttpClient.SendAsync(request);</div> <div>            response.EnsureSuccessStatusCode();</div> <div> </div> <div>            string result = await response.Content.ReadAsStringAsync();</div> <div>            onRespond(result);</div> <div>        }</div> <div>        catch (HttpRequestException ex)</div> <div>        {</div> <div>            Debug.LogError(ex);       //Unity3D console Debug</div> <div>            onRespond(null);</div> <div>        }</div> <div>    }</div> <div>Here is the Server Action:</div> <div> </div> <div>[Route("api/[controller]/[action]")]</div> <div>[ApiController]</div> <div>public class CalculatorController : ControllerBase</div> <div>{</div> <div>    public string AddMore([FromHeader]string numStr)</div> <div>    {</div> <div>        //string bodyStr;</div> <div>        //get string from Request.Body and set the value to bodyStr</div> <div>        return (int.Parse(numStr) + 10).ToString();</div> <div>    }</div> <div>}</div> <div>If I remove the line "request.Content = new StringContent("OK", Encoding.UTF8, "text/plain");" from the client method, the respond value is "15" which is correct.</div> <div> </div> <div>But with the request.Content, the client shows an error "An error occurred while sending the request ---> System.Net.WebException: The request requires buffering data to succeed". The server break point is not triggered, so the request was not sent out successfully.</div> <div> </div> <div>I have created another very simple server method using HttpListener, it reads the request.Content as clientContext stream correctly. I think maybe the problem is that request.Content is not equal to Http body, and it's unlikely a buffering issue as the error message says.</div> <div> </div> <div>My questions are, 1. How to send a string in Http body correctly, it's not argument and can be long (like a complete player profile in string format), so it's not proper for header or query or... 2. How can I receive and parse the string in the request body on server side correctly?</div> <div> </div> <div>Thank you so much for reading my post.</div>

Your post is jacked-up and is not readable.

Answer 2

User-1758582694 posted

I edited it several times, but the format is still a mess, but anyway, I re-created the project and the same method just worked .... I don't know why, but anyway, thanks for reading my thread.

The method is as below, people may try re-creating the project if you encounter the error message "An error occurred while sending the request ---> System.Net.WebException: The request requires buffering data to succeed". Hope it helps.

[Route("api/[controller]/[action]")]
[ApiController]
public class CalController : ControllerBase
{
public async Task<string> AddMore([FromHeader]string numStr)
{
string bodyMsg;
using (StreamReader stream = new StreamReader(Request.Body))
{
bodyMsg = await stream.ReadToEndAsync();
}
return (int.Parse(numStr) + 10).ToString() + " " + bodyMsg;
}
}

Answer 3

User1120430333 posted

I edited it several times, but the format is still a mess, but anyway, I re-created the project and the same method just worked .... I don't know why, but anyway, thanks for reading my thread.

The browser you are using has some kind of plugin software that's doing it. I suggest you use another browser to make post in the future,