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。

这可能有助于设置标题:

WebClient client = new WebClient();

string authInfo = this.credentials.UserName + ":" + this.credentials.Password;
authInfo = Convert.ToBase64String(Encoding.Default.GetBytes(authInfo));
client.Headers["Authorization"] = "Basic " + authInfo;

我是这样做的:

using (HttpClient httpClient = new HttpClient())
{
   Dictionary<string, string> tokenDetails = null;
   var messageDetails = new Message { Id = 4, Message1 = des };
   HttpClient client = new HttpClient();
   client.BaseAddress = new Uri("http://localhost:3774/");
   var login = new Dictionary<string, string>
       {
           {"grant_type", "password"},
           {"username", "sa@role.com"},
           {"password", "lopzwsx@23"},
       };
   var response = client.PostAsync("Token", new FormUrlEncodedContent(login)).Result;
   if (response.IsSuccessStatusCode)
   {
      tokenDetails = JsonConvert.DeserializeObject<Dictionary<string, string>>(response.Content.ReadAsStringAsync().Result);
      if (tokenDetails != null && tokenDetails.Any())
      {
         var tokenNo = tokenDetails.FirstOrDefault().Value;
         client.DefaultRequestHeaders.Add("Authorization", "Bearer " + tokenNo);
         client.PostAsJsonAsync("api/menu", messageDetails)
             .ContinueWith((postTask) => postTask.Result.EnsureSuccessStatusCode());
      }
   }
}

这个you-tube视频帮了我大忙。请查看一下。 https://www.youtube.com/watch?v=qCwnU06NV5Q

use UTF8选项

request.DefaultRequestHeaders.Authorization = 
new AuthenticationHeaderValue(
    "Basic", Convert.ToBase64String(
        System.Text.Encoding.UTF8.GetBytes(
           $"{yourusername}:{yourpwd}")));

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();
}

我建议你:

HttpClient.DefaultRequestHeaders.Add("Authorization", "Bearer <token>");

然后你可以这样使用它:

var response = await client.GetAsync(url);
if (response.IsSuccessStatusCode)
{
    responseMessage = await response.Content.ReadAsAsync<ResponseMessage>();
}