我正在尝试从Rest API获取数据。API需要3个东西来提供身份验证;
第一个是"接受：应用程序/vnd.###.v1.0 + json"
第二个："内容类型：应用程序/json "
第三个：Base64编码的"用户名：密码"字符串
我应该通过这些凭证的验证和授权自定义头。我知道有很多线程在这个网站上关于这个主题，但我不能解决他们的问题。
下面是代码块：

public class McAfeeIPSManager
{
    String URL = "https://serviceOfApi/sdkapi/session";

    public void getWebRequest()
    {
        System.Net.ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
        String username = "user";
        String password = "password1";

        var request = HttpWebRequest.Create(URL) as HttpWebRequest;
        request.Accept = "application/vnd.###.v2.0+json";
        request.Method = "GET";
        request.ContentType = "application/json";

        String encoded = System.Convert.ToBase64String(System.Text.Encoding.GetEncoding("ISO-8859-1").GetBytes(username + ":" + password));
        request.Headers.Add("Authorization","Basic "+encoded);


        try
        {
            // Get response  
            using (var response = request.GetResponse() as HttpWebResponse)
            {
                // Get the response stream  
                using (var responseReader = new StreamReader(response.GetResponseStream()))
                {
                    string responseBody = responseReader.ReadToEnd();

                    // Console application output  
                    System.Diagnostics.Debug.Write("Response Body ---> " + responseBody);
                    //Console.WriteLine(responseBody);
                }

           }
        }
        catch (WebException ex)
        {
            System.Diagnostics.Debug.Write("Error : " + ex.Message);
            Console.WriteLine("Error: {0}", ex.Message);
        }

    }
}

在这种情况下如何从WebAPI获取数据？有人能帮我吗？