What are the necessary changes required to work with TLS 1.1 in .NET framework 3.5 ?

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C#

ASP.NET

We have an asp.net application in .net framework 3.5 where we connect to the sales force service, but recently sales force have updated their security TLS 1.0 to higher version. So now we can not connect to sales force due to TLS vesrion updated. So how do we deal with TLS 1.1 or higher version through .net framework 3.5 ?

What I have tried:

On our local we have tried to update registry at HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols path for DWORD 32 bit . but it not worked for us.