Visual Studio无法发布Web App

Question

My ASP.NET web project is going to call the cURL using WebRequest I used to call PayPal's cURL to get the access token, hence I used the code below:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12 | SecurityProtocolType.Ssl3;

I can build the project and run in debug mode. However, when I click Publish, Visual Studio returns the following error.

'System.Net.SecurityProtocolType' does not contain a definition for 'Tls11'

I tried to use Visual Studio 2015 & 2017 to publish the web, but still not works.

For the background information: My project is running .NET Framework 4.5, Windows 10

Answer 1

This is a known issue with .NET framework 4.5 and has an open bug. The issue is that the compiler does not include the int enumeration for Tls11 .

Use this as a workaround:

const int SecurityProtocolTypeSsl3  = 48;
const int SecurityProtocolTypeTls11 = 768;
const int SecurityProtocolTypeTls12 = 3072;

ServicePointManager.SecurityProtocol |= (SecurityProtocolType)(SecurityProtocolTypeTls12 | SecurityProtocolTypeTls11 | SecurityProtocolTypeSsl3);