虽然最终版本的HttpContent和整个System.Net.Http命名空间将随.NET 4.5而来，但您可以通过从NuGet中添加Microsoft.Net.Http包来使用.NET 4版本

要获取6footunder的注释并将其转换为答案，HttpContent是抽象的，所以你需要使用一个派生类:

对于JSON Post:

var stringContent = new StringContent(json, Encoding.UTF8, "application/json");
var response = await httpClient.PostAsync("http://www.sample.com/write", stringContent);

Non-JSON:

var stringContent = new FormUrlEncodedContent(new[]
{
    new KeyValuePair<string, string>("field1", "value1"),
    new KeyValuePair<string, string>("field2", "value2"),
});
var response = await httpClient.PostAsync("http://www.sample.com/write", stringContent);

https://blog.pedrofelix.org/2012/01/16/the-new-system-net-http-classes-message-content/

就用微软。aspnet。webapi。client吧。

例子:

var client = HttpClientFactory.Create();
var result = await client.PostAsync<ExampleClass>("http://www.sample.com/write", new ExampleClass(), new JsonMediaTypeFormatter());

虽然最终版本的HttpContent和整个System.Net.Http命名空间将随.NET 4.5而来，但您可以通过从NuGet中添加Microsoft.Net.Http包来使用.NET 4版本

只使用……

var stringContent = new StringContent(jObject.ToString());
var response = await httpClient.PostAsync("http://www.sample.com/write", stringContent);

Or,

var stringContent = new StringContent(JsonConvert.SerializeObject(model), Encoding.UTF8, "application/json");
var response = await httpClient.PostAsync("http://www.sample.com/write", stringContent);