这适用于。net Core。 调用Soap客户端:

client.ClientCredentials.ServiceCertificate.SslCertificateAuthentication =
                new X509ServiceCertificateAuthentication()
                {
                    CertificateValidationMode = X509CertificateValidationMode.None,
                    RevocationMode = X509RevocationMode.NoCheck
                };  

在客户端配置中禁用ssl cert验证。

<behaviors>
   <endpointBehaviors>
      <behavior name="DisableSSLCertificateValidation">
         <clientCredentials>
             <serviceCertificate>
                <sslCertificateAuthentication certificateValidationMode="None" />
              </serviceCertificate>
           </clientCredentials>
        </behavior>

这适用于。net Core。 调用Soap客户端:

client.ClientCredentials.ServiceCertificate.SslCertificateAuthentication =
                new X509ServiceCertificateAuthentication()
                {
                    CertificateValidationMode = X509CertificateValidationMode.None,
                    RevocationMode = X509RevocationMode.NoCheck
                };  

为了进一步扩展bigignum的帖子-理想情况下，您需要一个解决方案，可以模拟您在生产中看到的条件，修改您的代码不会做到这一点，如果您忘记在部署之前将代码取出，则可能会带来危险。

您将需要某种类型的自签名证书。如果你知道你在做什么，你可以使用BIGNUM发布的二进制文件，但如果你不知道，你可以去寻找证书。如果你正在使用IIS Express，你已经有了其中一个，你只需要找到它。打开火狐或其他你喜欢的浏览器，进入你的开发网站。您应该能够从URL栏查看证书信息，并且根据您的浏览器，您应该能够将证书导出到一个文件。

接下来，打开MMC.exe，并添加Certificate管理单元。将证书文件导入“受信任的根证书颁发机构”存储区，这就是您所需要的全部内容。重要的是要确保它进入那个商店，而不是其他像“私人”的商店。如果您不熟悉MMC或证书，有许多网站提供如何做到这一点的信息。

现在，您的计算机作为一个整体将隐式地信任它自己生成的任何证书，您不需要添加代码来专门处理这一点。当您转移到生产环境时，它将继续工作，前提是您在那里安装了适当的有效证书。不要在生产服务器上这样做——那样会很糟糕，而且除了服务器上的客户端之外，它对任何其他客户端都不起作用。

IgnoreBadCertificates方法:

//I use a method to ignore bad certs caused by misc errors
IgnoreBadCertificates();

// after the Ignore call i can do what ever i want...
HttpWebRequest request_data = System.Net.WebRequest.Create(urlquerystring) as HttpWebRequest;

/*
and below the Methods we are using...
*/

/// <summary>
/// Together with the AcceptAllCertifications method right
/// below this causes to bypass errors caused by SLL-Errors.
/// </summary>
public static void IgnoreBadCertificates()
{
    System.Net.ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(AcceptAllCertifications);
}  

/// <summary>
/// In Short: the Method solves the Problem of broken Certificates.
/// Sometime when requesting Data and the sending Webserverconnection
/// is based on a SSL Connection, an Error is caused by Servers whoes
/// Certificate(s) have Errors. Like when the Cert is out of date
/// and much more... So at this point when calling the method,
/// this behaviour is prevented
/// </summary>
/// <param name="sender"></param>
/// <param name="certification"></param>
/// <param name="chain"></param>
/// <param name="sslPolicyErrors"></param>
/// <returns>true</returns>
private static bool AcceptAllCertifications(object sender, System.Security.Cryptography.X509Certificates.X509Certificate certification, System.Security.Cryptography.X509Certificates.X509Chain chain, System.Net.Security.SslPolicyErrors sslPolicyErrors)
{
    return true;
} 

这个代码对我有用。我必须添加TLS2，因为这是我感兴趣的URL正在使用的。

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
ServicePointManager.ServerCertificateValidationCallback +=
    (sender, cert, chain, sslPolicyErrors) => { return true; };
using (var client = new HttpClient())
{
    client.BaseAddress = new Uri(UserDataUrl);
    client.DefaultRequestHeaders.Accept.Clear();
    client.DefaultRequestHeaders.Accept.Add(new
      MediaTypeWithQualityHeaderValue("application/json"));
    Task<string> response = client.GetStringAsync(UserDataUrl);
    response.Wait();

    if (response.Exception != null)
    {
         return null;
    }

    return JsonConvert.DeserializeObject<UserData>(response.Result);
}