TLS 1.2 Security Protocol Support with different NET framework version

.Net 4.6 and above -You don’t need to do any additional work to support TLS 1.2, it’s supported by default.

.Net 4.5

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

.Net 4.0

ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;

.NET 3.5 (or below)

Visit https://mavenlink.zendesk.com/hc/en-us/articles/115007653028-Transport-Layer-Security-TLS