How to post data using HttpClient?

Question

I have got this HttpClient from Nuget.

When I want to get data I do it this way:

var response = await httpClient.GetAsync(url);
var data = await response.Content.ReadAsStringAsync();

But the problem is that I don't know how to post data? I have to send a post request and send these values inside it: comment="hello world" and questionId = 1. these can be a class's properties, I don't know.

Update I don't know how to add those values to HttpContent as post method needs it. httClient.Post(string, HttpContent);

You should follow the documentation for what content you should send in your post (if you are following an API). Then, just fill a HttpContent and use [PostAsync](http://msdn.microsoft.com/en-us/library/hh138190(v=vs.110).aspx) did you try that? — Patrick, Nov 15 '13 at 16:24
Btw, posting comments 10 minutes after posting your question with "can't anyone help?" and a smiley face will probably not encourage other overflowers to help you faster. If you don't find anyone answering your question you might want to look at your question and see what you can do to improve it, with more information about what you tried, instead of expecting everyone else to guess what you know. — Patrick, Nov 15 '13 at 16:28
@Patrick ok, I have updated it. please see if that is enough. — user2970840, Nov 15 '13 at 16:31
If someone is looking to upload a file using HttpClient - [C# HttpClient 4.5 multipart/form-data upload](https://stackoverflow.com/q/16416601/465053) — RBT, Sep 26 '19 at 08:59

score 216 · Answer 1 · edited Dec 22 '22 at 09:52

216

You need to use:

await client.PostAsync(uri, content);

Something like that:

var comment = "hello world";
var questionId = 1;

var formContent = new FormUrlEncodedContent(new[]
{
    new KeyValuePair<string, string>("comment", comment), 
    new KeyValuePair<string, string>("questionId", questionId) 
});

var myHttpClient = new HttpClient();
var response = await myHttpClient.PostAsync(uri.ToString(), formContent);

And if you need to get the response after post, you should use:

var stringContent = await response.Content.ReadAsStringAsync();

edited Dec 22 '22 at 09:52

starball

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answered Nov 15 '13 at 16:35

Icaro Bombonato

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response is `Unprocessable entry`. maybe I have a mistake somewhere else – user2970840 Nov 15 '13 at 17:03
18

or shorter dictionary literal: `var formContent = new FormUrlEncodedContent(new Dictionary { {"comment", comment}, {"questionId", questionId } });` – hkarask Feb 10 '17 at 14:30
Related post - [POSTing JsonObject With HttpClient From Web API](https://stackoverflow.com/q/6117101/465053) – RBT Sep 07 '21 at 04:21

score 8 · Answer 2 · edited Apr 06 '20 at 16:19

Try to use this:

using (var handler = new HttpClientHandler() { CookieContainer = new CookieContainer() })
{
    using (var client = new HttpClient(handler) { BaseAddress = new Uri("site.com") })
    {
        //add parameters on request
        var body = new List<KeyValuePair<string, string>>
        {
            new KeyValuePair<string, string>("test", "test"),
            new KeyValuePair<string, string>("test1", "test1")
        };

        HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, "site.com");

        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded; charset=UTF-8"));
        client.DefaultRequestHeaders.Add("Upgrade-Insecure-Requests", "1");
        client.DefaultRequestHeaders.Add("X-Requested-With", "XMLHttpRequest");
        client.DefaultRequestHeaders.Add("X-MicrosoftAjax", "Delta=true");
        //client.DefaultRequestHeaders.Add("Accept", "*/*");

        client.Timeout = TimeSpan.FromMilliseconds(10000);

        var res = await client.PostAsync("", new FormUrlEncodedContent(body));

        if (res.IsSuccessStatusCode)
        {
            var exec = await res.Content.ReadAsStringAsync();
            Console.WriteLine(exec);
        }                    
    }
}

You may want to use MultipartFormDataContent instead of FormUrlEncodedContent (that depends on what your server expects) — ed22, May 09 '21 at 10:53

score -2 · Answer 3 · edited Apr 06 '20 at 16:20

-2

Use UploadStringAsync method:

WebClient webClient = new WebClient();
webClient.UploadStringCompleted += (s, e) =>
{
    if (e.Error != null)
    {
        //handle your error here
    }
    else
    {
        //post was successful, so do what you need to do here
    }
};

webClient.UploadStringAsync(new Uri(yourUri), UriKind.Absolute), "POST", yourParameters);

edited Apr 06 '20 at 16:20

poke

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answered Nov 15 '13 at 16:37

Lori Lalonde - MSFT

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thanks, but I think this `HttpClient` is better than `WebClient`. easier and cleaner. isn't it? – user2970840 Nov 15 '13 at 16:45
Ah yes, I'm so used to WebClient, I had that in my head when I was reading the question. I haven't used HttpClient as of yet. Sorry! – Lori Lalonde - MSFT Nov 16 '13 at 01:32

How to post data using HttpClient?

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