如何为我的 HttpClient PostAsync 第二个参数设置 HttpContent？

Question

public static async Task<string> GetData(string url, string data)
{
    UriBuilder fullUri = new UriBuilder(url);

    if (!string.IsNullOrEmpty(data))
        fullUri.Query = data;

    HttpClient client = new HttpClient();

    HttpResponseMessage response = await client.PostAsync(new Uri(url), /*expects HttpContent*/);

    response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
    response.EnsureSuccessStatusCode();
    string responseBody = await response.Content.ReadAsStringAsync();

    return responseBody;
}

The PostAsync takes another parameter that needs to be HttpContent .

How do I set up an HttpContent ? There Is no documentation anywhere that works for Windows Phone 8.

If I do GetAsync , it works great! but it needs to be POST with the content of key="bla", something="yay"

//EDIT

Thanks so much for the answer... This works well, but still a few unsures here:

    public static async Task<string> GetData(string url, string data)
    {
        data = "test=something";

        HttpClient client = new HttpClient();
        StringContent queryString = new StringContent(data);

        HttpResponseMessage response = await client.PostAsync(new Uri(url), queryString );

        //response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
        response.EnsureSuccessStatusCode();
        string responseBody = await response.Content.ReadAsStringAsync();

        return responseBody;
    }

The data "test=something" I assumed would pick up on the api side as post data "test", evidently it does not. On another matter, I may need to post entire objects/arrays through post data, so I assume json will be best to do so. Any thoughts on how I get post data through?

Perhaps something like:

class SomeSubData
{
    public string line1 { get; set; }
    public string line2 { get; set; }
}

class PostData
{
    public string test { get; set; }
    public SomeSubData lines { get; set; }
}

PostData data = new PostData { 
    test = "something",
    lines = new SomeSubData {
        line1 = "a line",
        line2 = "a second line"
    }
}
StringContent queryString = new StringContent(data); // But obviously that won't work

Answer 1

This is answered in some of the answers to Can't find how to use HttpContent as well as in this blog post .

In summary, you can't directly set up an instance of HttpContent because it is an abstract class . You need to use one the classes derived from it depending on your need. Most likely StringContent , which lets you set the string value of the response, the encoding, and the media type in the constructor. See: http://msdn.microsoft.com/en-us/library/system.net.http.stringcontent.aspx

Answer 2

To add to Preston's answer, here's the complete list of the HttpContent derived classes available in the standard library:

Credit : https://pfelix.wordpress.com/2012/01/16/the-new-system-net-http-classes-message-content/

There's also a supposed ObjectContent but I was unable to find it in ASP.NET Core .

Of course, you could skip the whole HttpContent thing all together with Microsoft.AspNet.WebApi.Client extensions (you'll have to do an import to get it to work in ASP.NET Core for now: https://github.com/aspnet/Home/issues/1558 ) and then you can do things like:

var response = await client.PostAsJsonAsync("AddNewArticle", new Article
{
    Title = "New Article Title",
    Body = "New Article Body"
});

Answer 3

    public async Task<ActionResult> Index()
    {
        apiTable table = new apiTable();
        table.Name = "Asma Nadeem";
        table.Roll = "6655";

        string str = "";
        string str2 = "";

        HttpClient client = new HttpClient();

        string json = JsonConvert.SerializeObject(table);

        StringContent httpContent = new StringContent(json, System.Text.Encoding.UTF8, "application/json");

        var response = await client.PostAsync("http://YourSite.com/api/apiTables", httpContent);

        str = "" + response.Content + " : " + response.StatusCode;

        if (response.IsSuccessStatusCode)
        {       
            str2 = "Data Posted";
        }

        return View();
    }