TLS 1.2 not negotiated in .NET 4.7 without explicit ServicePointManager.SecurityProtocol call

Question

I need to upgrade a .NET application to support a call to an API on a website that only supports TLS 1.2. From what I read, if the application is targeting 4.6 or higher the

Answer 1

I had the same issue (Windows 10 and SSL3 / TLS only... not System Default) with a legacy app targeting 4.7.2. My issue was that during the upgrade process over the years we never added in the targetFramework to the system.web > httpRuntime element (Note: it did exist on system.web > compilation element). Before taking bigger steps, ensure your system.web looks something like the following:

In the above example, swap 4.7.2 for whatever version of the framework you are currently using that is >= 4.7.