对我来说，问题是我试图将IIS作为web服务部署在服务器上，我在服务器上安装了证书，但运行IIS的用户对证书没有正确的权限。

如何给ASP。NET访问证书存储中的证书中的私钥?

我终于找到了答案(我没有注明我的来源，但它来自一次搜索);

虽然代码在Windows XP中工作，但在Windows 7中，你必须在开头添加这个:

// using System.Net;
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
// Use SecurityProtocolType.Ssl3 if needed for compatibility reasons

现在，它工作得很完美。

齿顶高

Robin French提到过;如果你在配置PayPal时遇到了这个问题，请注意从2018年12月3日开始他们将不支持SSL3。您需要使用TLS。这是关于它的Paypal页面。

这一个是为我工作在MVC webclient

public string DownloadSite(string RefinedLink)
{
    try
    {
        Uri address = new Uri(RefinedLink);

        ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;

        System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

        using (WebClient webClient = new WebClient())
        {
            var stream = webClient.OpenRead(address);
            using (StreamReader sr = new StreamReader(stream))
            {
                var page = sr.ReadToEnd();

                return page;
            }
        }

    }
    catch (Exception e)
    {
        log.Error("DownloadSite - error Lin = " + RefinedLink, e);
        return null;
    }
}

In my case, I was running under Visual Studio 2022. Time and time again I was getting this error. Going through the code I saw that it retrieved the certificate just fine. Security was set to TLS1.2, both answers above. For whatever reason, running Visual Studio as Administrator made it work! Maybe someone can explain to me how the code retrieved the certificate from the store just fine. I could see it and all the properties. Why in the name of this world would it not process the request unless I run VS in admin mode???

我最近也遇到了同样的问题。我的环境运行在。net 4.6.1和VB.NET下。这就是我解决问题的方法:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3
ServicePointManager.ServerCertificateValidationCallback = New RemoteCertificateValidationCallback(AddressOf util.ValidateServerCertificate)

还有util。ValidateServerCertificate函数为:

Public Function ValidateServerCertificate(ByVal sender As Object, ByVal certificate As X509Certificate, ByVal chain As X509Chain, ByVal sslPolicyErrors As SslPolicyErrors) As Boolean
    Return True
End Function

After days of pulling what hair I have left out, we solved the problem. I tried everything suggested on this post and nothing worked for me. For us, we had a basic .Net Framework 4.8 console app running on a customers Windows VM. The on-premise server we were communicating with required that SSL Certificate Validation was turned off. One of our guys discovered that the server required we were using TLS 1.0 and on the registry settings of the VM, TLS 1.0 was disabled. Once we enabled that, it worked. I also needed to added the following two lines as mentioned many times above:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };