4 個解決辦法，我用的第四個方法就解決了， 注冊表手動添加的 重啟后不管用，第四個方法 直接用程序改一下方便
首先得保證服務器是否支持 tls1.2 去注冊表里查或者百度怎么查,基本大多數都用的是1.2
1.
代碼前加這個
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, errors) => true;
或者 ServicePointManager.SecurityProtocol = (SecurityProtocolType)192 | (SecurityProtocolType)768 | (SecurityProtocolType)3072;
或者ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3
| SecurityProtocolType.Tls
| (SecurityProtocolType)0x300 //Tls11
| (SecurityProtocolType)0xC00; //Tls12
2. 復制下面注冊表代碼導入到注冊表。新建txt，將后綴txt改為reg（注冊表項），導入
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp]
"DefaultSecureProtocols"=dword:00000800
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp]
"DefaultSecureProtocols"=dword:00000800
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Client]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001
3. 升級 到 fromwork4.6 版本
4.
https://www.nartac.com/Products/IISCrypto/Download
去下載這個軟件 打開軟件后 都選上確定 重啟就好了
