public class ApiTestController : ApiController
{
 // GET api/<controller>/5
 public object Get(int id)
 {
  return "value" + id;
 }
}

ApiTestController

 //
 // 摘要:
 //  A base type for handlers which only do some small processing of request and/or
 //  response messages.
 public abstract class MessageProcessingHandler : DelegatingHandler
 {
  //
  // 摘要:
  //  Creates an instance of a System.Net.Http.MessageProcessingHandler class.
  protected MessageProcessingHandler();
  //
  // 摘要:
  //  Creates an instance of a System.Net.Http.MessageProcessingHandler class with
  //  a specific inner handler.
  //
  // 參數(shù):
  // innerHandler:
  //  The inner handler which is responsible for processing the HTTP response messages.
  protected MessageProcessingHandler(HttpMessageHandler innerHandler);

  //
  // 摘要:
  //  Performs processing on each request sent to the server.
  //
  // 參數(shù):
  // request:
  //  The HTTP request message to process.
  //
  // cancellationToken:
  //  A cancellation token that can be used by other objects or threads to receive
  //  notice of cancellation.
  //
  // 返回結(jié)果:
  //  Returns System.Net.Http.HttpRequestMessage.The HTTP request message that was
  //  processed.
  protected abstract HttpRequestMessage ProcessRequest(HttpRequestMessage request, CancellationToken cancellationToken);
  //
  // 摘要:
  //  Perform processing on each response from the server.
  //
  // 參數(shù):
  // response:
  //  The HTTP response message to process.
  //
  // cancellationToken:
  //  A cancellation token that can be used by other objects or threads to receive
  //  notice of cancellation.
  //
  // 返回結(jié)果:
  //  Returns System.Net.Http.HttpResponseMessage.The HTTP response message that was
  //  processed.
  protected abstract HttpResponseMessage ProcessResponse(HttpResponseMessage response, CancellationToken cancellationToken);
  //
  // 摘要:
  //  Sends an HTTP request to the inner handler to send to the server as an asynchronous
  //  operation.
  //
  // 參數(shù):
  // request:
  //  The HTTP request message to send to the server.
  //
  // cancellationToken:
  //  A cancellation token that can be used by other objects or threads to receive
  //  notice of cancellation.
  //
  // 返回結(jié)果:
  //  Returns System.Threading.Tasks.Task`1.The task object representing the asynchronous
  //  operation.
  //
  // 異常:
  // T:System.ArgumentNullException:
  //  The request was null.
  protected internal sealed override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken);
 }

MessageProcessingHandler

/// <summary>
 /// 加密解密接口
 /// </summary>
 public interface IMessageEnCryption
 {
  /// <summary>
  /// 加密
  /// </summary>
  /// <param name="content"></param>
  /// <returns></returns>
  string Encode(string content);
  /// <summary>
  /// 解密
  /// </summary>
  /// <param name="content"></param>
  /// <returns></returns>
  string Decode(string content);
 }

IMessageEnCryption

/// <summary>
 /// 加解密 只做 base64
 /// </summary>
 public class MessageEncryptionVersion1_0 : IMessageEnCryption
 {
  public string Decode(string content)
  {
   return content?.DecryptBase64();
  }

  public string Encode(string content)
  {
   return content.EncryptBase64();
  }
 }

MessageEncryptionVersion1_0

/// <summary>
 /// 數(shù)據(jù)加解密 des
 /// </summary>
 public class MessageEncryptionVersion1_1 : IMessageEnCryption
 {
  public static readonly string KEY = "fHil/4]0";
  public string Decode(string content)
  {
   return content.DecryptDES(KEY);
  }
  public string Encode(string content)
  {
   return content.EncryptDES(KEY);
  }
 }

MessageEncryptionVersion1_1

public static class EncrypExtends
 {
  //默認密鑰向量
  private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
  internal static string Key = "*@&$(@#H";

  //// <summary>
  /// DES加密字符串
  /// </summary>
  /// <param name="encryptString">待加密的字符串</param>
  /// <param name="encryptKey">加密密鑰,要求為8位</param>
  /// <returns>加密成功返回加密后的字符串，失敗返回源串</returns>
  public static string EncryptDES(this string encryptString, string encryptKey)
  {
   try
   {
    byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
    byte[] rgbIV = Keys;
    byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
    DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
    MemoryStream mStream = new MemoryStream();
    CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
    cStream.Write(inputByteArray, 0, inputByteArray.Length);
    cStream.FlushFinalBlock();
    return Convert.ToBase64String(mStream.ToArray());
   }
   catch
   {
    return encryptString;
   }
  }
  //// <summary>
  /// DES解密字符串
  /// </summary>
  /// <param name="decryptString">待解密的字符串</param>
  /// <param name="decryptKey">解密密鑰,要求為8位,和加密密鑰相同</param>
  /// <returns>解密成功返回解密后的字符串，失敗返源串</returns>
  public static string DecryptDES(this string decryptString, string key)
  {
   try
   {
    byte[] rgbKey = Encoding.UTF8.GetBytes(key.Substring(0, 8));
    byte[] rgbIV = Keys;
    byte[] inputByteArray = Convert.FromBase64String(decryptString);
    DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
    MemoryStream mStream = new MemoryStream();
    CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
    cStream.Write(inputByteArray, 0, inputByteArray.Length);
    cStream.FlushFinalBlock();
    return Encoding.UTF8.GetString(mStream.ToArray());
   }
   catch
   {
    return decryptString;
   }
  }
  public static string EncryptBase64(this string encryptString)
  {
   return Convert.ToBase64String(Encoding.UTF8.GetBytes(encryptString));
  }
  public static string DecryptBase64(this string encryptString)
  {
   return Encoding.UTF8.GetString(Convert.FromBase64String(encryptString));
  }
  public static string DecodeUrl(this string cryptString)
  {
   return System.Web.HttpUtility.UrlDecode(cryptString);
  }
  public static string EncodeUrl(this string cryptString)
  {
   return System.Web.HttpUtility.UrlEncode(cryptString);
  }
 }

EncrypExtends

/// <summary>
 /// API消息請求處理
 /// </summary>
 public class JoyMessageHandler : MessageProcessingHandler
 {
  /// <summary>
  /// 接收到request時 處理
  /// </summary>
  /// <param name="request"></param>
  /// <param name="cancellationToken"></param>
  /// <returns></returns>
  protected override HttpRequestMessage ProcessRequest(HttpRequestMessage request, CancellationToken cancellationToken)
  {
   if (request.Content.IsMimeMultipartContent())
    return request;
   // 獲取請求頭中 api_version版本號
   var ver = System.Web.HttpContext.Current.Request.Headers.GetValues("api_version")?.FirstOrDefault();
   // 根據(jù)api_version版本號獲取加密對象, 如果為null 則不需要加密
   var encrypt = MessageEncryptionCreator.GetInstance(ver);
   if (encrypt != null)
   {
    // 讀取請求body中的數(shù)據(jù)
    string baseContent = request.Content.ReadAsStringAsync().Result;
    // 獲取加密的信息
    // 兼容 body: 加密數(shù)據(jù) 和 body: code=加密數(shù)據(jù)
    baseContent = baseContent.Match("(code=)*(?<code>[\\S]+)", 2);
    // URL解碼數(shù)據(jù)
    baseContent = baseContent.DecodeUrl();
    // 用加密對象解密數(shù)據(jù)
    baseContent = encrypt.Decode(baseContent);
    string baseQuery = string.Empty;
    if (!request.RequestUri.Query.IsNullOrEmpty())
    {
     // 同 body
     // 讀取請求 url query數(shù)據(jù)
     baseQuery = request.RequestUri.Query.Substring(1);
     baseQuery = baseQuery.Match("(code=)*(?<code>[\\S]+)", 2);
     baseQuery = baseQuery.DecodeUrl();
     baseQuery = encrypt.Decode(baseQuery);
    }
    // 將解密后的 URL 重置URL請求
    request.RequestUri = new Uri($"{request.RequestUri.AbsoluteUri.Split('?')[0]}?{baseQuery}");
    // 將解密后的BODY數(shù)據(jù) 重置
    request.Content = new StringContent(baseContent);
   }
   return request;
  }
  /// <summary>
  /// 處理將要向客戶端response時
  /// </summary>
  /// <param name="response"></param>
  /// <param name="cancellationToken"></param>
  /// <returns></returns>
  protected override HttpResponseMessage ProcessResponse(HttpResponseMessage response, CancellationToken cancellationToken)
  {
   //var isMediaType = response.Content.Headers.ContentType.MediaType.Equals(mediaTypeName, StringComparison.OrdinalIgnoreCase);
   var ver = System.Web.HttpContext.Current.Request.Headers.GetValues("api_version")?.FirstOrDefault();
   var encrypt = MessageEncryptionCreator.GetInstance(ver);
   if (encrypt != null)
   {
    if (response.StatusCode == HttpStatusCode.OK)
    {
     var result = response.Content.ReadAsStringAsync().Result;
     // 返回消息 進行加密
     var encodeResult = encrypt.Encode(result);
     response.Content = new StringContent(encodeResult);
    }
   }
   return response;
  }
 }

JoyMessageHandler

public static class WebApiConfig
 {
  public static void Register(HttpConfiguration config)
  {
   // Web API 配置和服務
   // 將 Web API 配置為僅使用不記名令牌身份驗證。
   config.SuppressDefaultHostAuthentication();
   config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));
   // Web API 路由
   config.MapHttpAttributeRoutes();
   config.Routes.MapHttpRoute(
    name: "DefaultApi",
    routeTemplate: "api/{controller}/{id}",
    defaults: new { id = RouteParameter.Optional }
   );
   // 添加自定義消息處理
   config.MessageHandlers.Add(new JoyMessageHandler());
  }
 }

WebApiConfig

[TestMethod()]
  public void GetTest()
  {
   var id = 10;
   var resultSuccess = $"\"value{id}\"";
   //不加密
   Trace.WriteLine($"without encryption.");
   var url = $"api/ApiTest?id={id}";
   Trace.WriteLine($"get url : {url}");
   var response = http.GetAsync(url).Result;
   var result = response.Content.ReadAsStringAsync().Result;
   Assert.AreEqual(result, resultSuccess);
   Trace.WriteLine($"result : {result}");
   //使用 方案1加密
   Trace.WriteLine($"encryption case one.");
   url = $"api/ApiTest?code=" + $"id={id}".EncryptBase64().EncodeUrl();
   Trace.WriteLine($"get url : {url}");
   http.DefaultRequestHeaders.Clear();
   http.DefaultRequestHeaders.Add("api_version", "1.0");
   response = http.GetAsync(url).Result;
   result = response.Content.ReadAsStringAsync().Result;
   Trace.WriteLine($"result : {result}");
   result = result.DecryptBase64();
   Trace.WriteLine($"DecryptBase64 : {result}");
   Assert.AreEqual(result, resultSuccess);
   //使用 方案2 加密通訊
   Trace.WriteLine($"encryption case one.");
   url = $"api/ApiTest?code=" + $"id={id}".EncryptDES(MessageEncryptionVersion1_1.KEY).EncodeUrl();
   Trace.WriteLine($"get url : {url}");
   http.DefaultRequestHeaders.Clear();
   http.DefaultRequestHeaders.Add("api_version", "1.1");
   response = http.GetAsync(url).Result;
   result = response.Content.ReadAsStringAsync().Result;
   Trace.WriteLine($"result : {result}");
   result = result.DecryptDES(MessageEncryptionVersion1_1.KEY);
   Trace.WriteLine($"DecryptBase64 : {result}");
   Assert.AreEqual(result, resultSuccess);
  }

ApiTestControllerTests