在 .NET 中使用 WebClient 发送 PATCH 请求

Question

I have an older ASP.NET WebForms site. I am trying to use WebClient to send a PATCH request to a REST API:

using (WebClient client = new WebClient())
{
    client.Headers[HttpRequestHeader.Authorization] = "Bearer " + authToken;
    try
    {
        responseString = Encoding.UTF8.GetString(client.UploadValues(endpoint, "PATCH", body));
    }                
    catch (Exception e)
    {
        return e;
    }            
}

In this snippet, endpoint is the URI I'm PATCH -ing to, and body is a NameValueCollection .

This gives me an HTTP 400 "Bad Request" error. If I drill down in the exception, it indicates a protocol violation. I have tried adding a header for content-type, but that did not help.

This same code does work for POST requests, and it's how I'm getting my access token successfully. But it does not work for PATCH . Is there any way to send a valid PATCH request using WebClient ?

I realize there are other libraries out there, but if possible, I'd like to be consistent with the rest of the code in this class in using WebClient . If I have to switch to something else, I'd want to update the rest of the code too.

Update

Yes, the API does support PATCH . It's the Microsoft Graph API and PATCH works fine with Postman.

Answer 1

It looks ok. If the API supports PATCH you should receive a response. Could you check if PATCH is implemented on the API?
Another possibility is that you violate some validation rules applied in PATCH method.

Answer 2

I got it to work using the UploadString method, as follows:

using (WebClient client = new WebClient())
{
    client.Headers[HttpRequestHeader.Authorization] = "Bearer " + authToken;
    try
    {
        client.Headers[HttpRequestHeader.ContentType] = "application/json";
        responseString = client.UploadString(endpoint, method, body);
    }                
    catch (Exception e)
    {
        return e;
    }            
}

Where body is a JSON-formatted string, instead of a NameValueCollection as I was trying initially. I'm not sure if there's a better way to do this, but it seems to be working now.