public static string SignDemo(string data)
{
    byte[] byKey = "sy%3dz$p";
    byte[] byIV = "sy%3dz$p";
    using (DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider())
    using (MemoryStream ms = new MemoryStream())
    using (CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey, byIV), CryptoStreamMode.Write))
    using (StreamWriter sw = new StreamWriter(cst))
    {
        sw.Write(data);
        sw.Flush();
        cst.FlushFinalBlock();
        sw.Flush();
        byKey = byIV = null;
        return Convert.ToBase64String(ms.GetBuffer(),0,(int)ms.Length);
    }
}

public static string RequestDemo(string data)
{
    // 公共参数
    string url = "http://localhost:8906/zh-CN/api/Service/CommonService";
    ExtServiceRequest request = new ExtServiceRequest();
    request.RequestId = Guid.NewGuid().ToString();
    request.RequestTime = DateTimeHelper.GetNowDateTime();
    request.Version = "1.0.0.1";
    request.AppToken = "o5Nf65FiKgoQu1df1jI1syOmVZQJyCPn";
    // 业务参数
    SupplierQueryCompatibleTemplateRequest inRequest = new SupplierQueryCompatibleTemplateRequest();
    inRequest.StartTrDateTime = DateTimeHelper.GetNowDateTime().AddYears(-1);
    inRequest.EndTrDateTime = DateTimeHelper.GetNowDateTime();
    string inRequestJson = SerializableConvert.SerializeObject(inRequest);
    request.Message = inRequestJson;
    // 接口名称
    request.MessageType = "SupplierQueryCompatibleTemplate";
    // 签名
    string json = SerializableConvert.SerializeObject(request);
    string data = EncryHelper.GetEncodeString(json);
    request.Sign = data;
    // 发起请求
    HttpClient client = new HttpClient();
    HttpResponseMessage responseMessage = client.PostAsJsonAsync(url, request).Result;
    string responseContent = responseMessage.Content.ReadAsStringAsync().Result;
    // 解析响应数据
    ExtServiceResponse response = SerializableConvert.DeserializeObject<ExtServiceResponse>(responseContent);
    ExtCategoryResponse extResponse = SerializableConvert.DeserializeObject<ExtCategoryResponse>(response.Message);
}