Force TLS 1.2 with WebClient

In .NET Framework 4.0+, use this StackOverflow answer to disable TLS 1.0 and force 1.1 or 1.2:

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

In prior .NET Framework versions, you can force it without the enum value:

public const SslProtocols _Tls12 = (SslProtocols)0x00000C00;
public const SecurityProtocolType Tls12 = (SecurityProtocolType)_Tls12;
ServicePointManager.SecurityProtocol = Tls12;