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 did you try that? — Patrick
– Patrick, Commented Nov 15, 2013 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
– Patrick, Commented Nov 15, 2013 at 16:28
@Patrick ok, I have updated it. please see if that is enough. — user2970840
– user2970840, Commented Nov 15, 2013 at 16:31
If someone is looking to upload a file using HttpClient - C# HttpClient 4.5 multipart/form-data upload — RBT
– RBT, Commented Sep 26, 2019 at 8:59

starball · Accepted Answer · 2022-12-22 09:52:10Z

237

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, 2022 at 9:52

starball♦

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answered Nov 15, 2013 at 16:35

Icaro Bombonato

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5 Comments

user2970840 Over a year ago

response is Unprocessable entry. maybe I have a mistake somewhere else

hkarask Over a year ago

or shorter dictionary literal:

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

RBT Over a year ago

Related post - POSTing JsonObject With HttpClient From Web API

D. Ror. Over a year ago

Thank you for this FormUrlEncodedContent answer! I was trying to do a .PostAsync() with MultiPartFormDataContent and got a response that it couldn't be parsed as Form Data.

Shane Over a year ago

@D.Ror. That makes sense, as FormUrlEncodedContent is application/x-www-form-urlencoded content type, while MultipartFormDataContent is multipart/form-data. These are not the same.

poke · Accepted Answer · 2020-04-06 16:19:40Z

9

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);
        }                    
    }
}

edited Apr 6, 2020 at 16:19

poke

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answered Jun 12, 2019 at 15:41

L.Zoffoli

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1 Comment

ed22 Over a year ago

You may want to use MultipartFormDataContent instead of FormUrlEncodedContent (that depends on what your server expects)

poke · Accepted Answer · 2020-04-06 16:20:13Z

-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 6, 2020 at 16:20

poke

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answered Nov 15, 2013 at 16:37

Lori Lalonde - MSFT

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2 Comments

user2970840 Over a year ago

thanks, but I think this HttpClient is better than WebClient. easier and cleaner. isn't it?

Lori Lalonde - MSFT Over a year ago

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!

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