Update .NET web service to use TLS 1.2

Add the following code before you instantiate your web service client:

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

Or for backward compatibility with TLS 1.1 and prior:

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

We actually just upgraded a .NET web service to 4.6 to allow TLS 1.2.

What Artem is saying were the first steps we've done. We recompiled the framework of the web service to 4.6 and we tried change the registry key to enable TLS 1.2, although this didn't work: the connection was still in TLS 1.0. Also, we didn't want to disallow SLL 3.0, TLS 1.0 or TLS 1.1 on the machine: other web services could be using this; we rolled-back our changes on the registry.

We actually changed the Web.Config files to tell IIS: "hey, run me in 4.6 please".

Here's the changes we added in the web.config + recompilation in .NET 4.6:

<system.web>
    <compilation targetFramework="4.6"/> <!-- Changed framework 4.0 to 4.6 -->

    <!--Added this httpRuntime -->
    <httpRuntime targetFramework="4.6" />

    <authentication mode="Windows"/>
    <pages controlRenderingCompatibilityVersion="4.0"/>
</system.web>

And the connection changed to TLS 1.2, because IIS is now running the web service in 4.6 (told explicitly) and 4.6 is using TLS 1.2 by default.

if you're using .Net earlier than 4.5 you wont have Tls12 in the enum so state is explicitly mentioned here

ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;