It seems that support for TLS 1.2 dependent on the .net framework version.
- NET 4.6 and above. Supported by default.
- .NET 4.5. TLS 1.2 is supported. The following code will make TLS 1.2 to be used as the default protocol. ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
- .NET 4.0. TLS 1.2 is not supported, but following code can be used as a workaround:
ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;
- .NET 3.5 or below. TLS 1.2 is not supported.