C#: HttpClient with POST parameters

Question

I use codes below to send POST request to a server:

string url = "http://myserver/method?param1=1&param2=2"    
HttpClientHandler handler = new HttpClientHandler();
HttpClient httpClient = new HttpClient(handler);
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, url);
HttpResponseMessage response = await httpClient.SendAsync(request);

I don't have access to the server to debug but I want to know, is this request sent as POST or GET?

If it is GET, How can I change my code to send param1 & param2 as POST data (not in the URL)?

Solution

A cleaner alternative would be to use a Dictionary to handle parameters. They are key-value pairs after all.

private static readonly HttpClient httpclient;

static MyClassName()
{
    // HttpClient is intended to be instantiated once and re-used throughout the life of an application. 
    // Instantiating an HttpClient class for every request will exhaust the number of sockets available under heavy loads. 
    // This will result in SocketException errors.
    // https://docs.microsoft.com/en-us/dotnet/api/system.net.http.httpclient?view=netframework-4.7.1
    httpclient = new HttpClient();    
} 

var url = "http://myserver/method";
var parameters = new Dictionary<string, string> { { "param1", "1" }, { "param2", "2" } };
var encodedContent = new FormUrlEncodedContent (parameters);

var response = await httpclient.PostAsync (url, encodedContent).ConfigureAwait (false);
if (response.StatusCode == HttpStatusCode.OK) {
    // Do something with response. Example get content:
    // var responseContent = await response.Content.ReadAsStringAsync ().ConfigureAwait (false);
}

Also dont forget to Dispose() httpclient, if you dont use the keyword using

As stated in the Remarks section of the HttpClient class in the Microsoft docs, HttpClient should be instantiated once and re-used.

Edit:

You may want to look into response.EnsureSuccessStatusCode(); instead of if (response.StatusCode == HttpStatusCode.OK).

You may want to keep your httpclient and dont Dispose() it. See: Do HttpClient and HttpClientHandler have to be disposed?

Edit:

Do not worry about using .ConfigureAwait(false) in .NET Core. For more details look at https://blog.stephencleary.com/2017/03/aspnetcore-synchronization-context.html

Comments

[Mark Szabo]

@JohnCroneh this isn't working anymore. Please accept the other answer below!

[R. McManaman]

@JohnCroneh please change the accepted answer to one that works

[HellBaby]

@R.McManaman Actually it's a good answer if you would go with creating an no known method type. It's missing some "using" to make sure that it disposes and a "make sure it's converted", but it follows the PostAsync wrapper implementation.

[d00d]

That version does not work for me. The parameter received by the controller action is always null.

[aloisdg]

@d00d feel free to post a new question linked to this one explaining your problem.

[Hosein Aqajani]

and what about sending Get request by parameters?

[aloisdg]

@HoseinAqajani I think it would be a great question to ask in a new post. Feel free to link it here as comment.

[Beltway]

List<KeyValuePair<string, string>> is more concise as query parameter keys aren't necessarily unique.

[aloisdg]

While you are true (so here is an upvote), I dont like query parameter with duplicate. I dont only code in .net and since there is no spec about this, different server handle duplicate differently. Beside, duplicate can lead to HPP.