使用基本授权和Json参数。

using (HttpClient client = new HttpClient())
{
    var request_json = "your json string";

    var content = new StringContent(request_json, Encoding.UTF8, "application/json");

    var authenticationBytes = Encoding.ASCII.GetBytes("YourUsername:YourPassword");

    client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic",
            Convert.ToBase64String(authenticationBytes));
    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    var result = await client.PostAsync("YourURL", content);

    var result_string = await result.Content.ReadAsStringAsync();
}

6年过去了，但为了帮助别人，我加了这个。

https://www.codeproject.com/Tips/996401/Authenticate-WebAPIs-with-Basic-and-Windows-Authen

var authenticationBytes = Encoding.ASCII.GetBytes("<username>:<password>");
using (HttpClient confClient = new HttpClient())
{
  confClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", 
         Convert.ToBase64String(authenticationBytes));
  confClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(Constants.MediaType));  
  HttpResponseMessage message = confClient.GetAsync("<service URI>").Result;
  if (message.IsSuccessStatusCode)
  {
    var inter = message.Content.ReadAsStringAsync();
    List<string> result = JsonConvert.DeserializeObject<List<string>>(inter.Result);
  }
}

Firstly, I wouldn't use HttpClient directly. It's too easy to make mistakes - particularly in the area of headers. The DefaultHeadersCollection is not immutable and not thread-safe because other parts of the app can change the headers on you. It's best to set the headers when you make the call. If you are working with an abstraction, and that is recommended because the classes in this area are a bit of a mess, you would want to have a headers collection and put those on your HttpRequestMessage before you send it. You need to make sure you put the content headers on the content, and not the message.

代码引用

foreach (var headerName in request.Headers.Names)
{
    //"Content-Type"
    if (string.Compare(headerName, HeadersExtensions.ContentTypeHeaderName, StringComparison.OrdinalIgnoreCase) == 0)
    {
        //Note: not sure why this is necessary...
        //The HttpClient class seems to differentiate between content headers and request message headers, but this distinction doesn't exist in the real world...
        //TODO: Other Content headers
        httpContent?.Headers.Add(HeadersExtensions.ContentTypeHeaderName, request.Headers[headerName]);
    }
    else
    {
        httpRequestMessage.Headers.Add(headerName, request.Headers[headerName]);
    }
}

下面是一个数据结构，您可以使用它来发送包含头部的请求。

代码引用

public interface IRequest
{
    CancellationToken CancellationToken { get; }
    string? CustomHttpRequestMethod { get; }
    IHeadersCollection Headers { get; }
    HttpRequestMethod HttpRequestMethod { get; }
    AbsoluteUrl Uri { get; }
}

public interface IRequest<TBody> : IRequest
{
    TBody? BodyData { get; }
}

和，一个头文件集合:

代码引用

public sealed class HeadersCollection : IHeadersCollection
{
    #region Fields
    private readonly IDictionary<string, IEnumerable<string>> dictionary;
    #endregion

    #region Public Constructors

    public HeadersCollection(IDictionary<string, IEnumerable<string>> dictionary) => this.dictionary = dictionary;

    public HeadersCollection(string key, string value) : this(ImmutableDictionary.CreateRange(
                new List<KeyValuePair<string, IEnumerable<string>>>
                {
                    new(key, ImmutableList.Create(value))
                }
                ))
    {
    }

    #endregion Public Constructors

    #region Public Properties
    public static HeadersCollection Empty { get; } = new HeadersCollection(ImmutableDictionary.Create<string, IEnumerable<string>>());
    public IEnumerable<string> Names => dictionary.Keys;
    IEnumerable<string> IHeadersCollection.this[string name] => dictionary[name];
    #endregion Public Properties

    #region Public Methods
    public bool Contains(string name) => dictionary.ContainsKey(name);

    public IEnumerator<KeyValuePair<string, IEnumerable<string>>> GetEnumerator() => dictionary.GetEnumerator();

    IEnumerator IEnumerable.GetEnumerator() => dictionary.GetEnumerator();
    public override string ToString() => string.Join("\r\n", dictionary.Select(kvp => $"{kvp.Key}: {string.Join(", ", kvp.Value)}\r\n"));
    #endregion
}

在这里查看所有工作代码和示例。

如果您正在使用Visual Studio IISExpress调试模式并连接到HTTP端口而不是HTTPS端口，您可能会发现身份验证头被删除。

切换到SLL连接，它们将再次出现。

不确定原因，可能是设置重定向HTTP流量，导致身份验证被删除。

对于性能和端口耗尽问题，重用HttpClient实例是一个很好的实践，而且因为没有一个答案给出了这个解决方案(甚至会把你引向糟糕的实践:)，所以我在这里放了一个链接，指向我对类似问题的回答:

https://stackoverflow.com/a/40707446/717372

一些关于如何正确使用HttpClient的源代码:

https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/ https://blogs.msdn.microsoft.com/alazarev/2017/12/29/disposable-finalizers-and-httpclient/

Oauth流程是复杂的，总是有一个或另一个错误的空间。 我的建议是始终使用样板代码和一组用于OAuth身份验证流的库。这会让你的生活更轻松。

下面是库集的链接。用于。net的OAuth库