Azure support of .NET 3.5 Sp1 and .NET 4.0 since Guest OS 1.2
Since Azure Guest OS 1.2 both .NET 3.5 SP1 and .NET 4.0 are supported. The default version for the Azure Guest OS (currently @ 1.5) is .NET 3.5 SP1 and we have plans to switch to .NET 4 as the default framework at a future date.
As documented, there is already one area of compatibility documented – which is around ASP.NET performance counters. If you are you are using .NET Performance counters for your diagnostics information, you need to use version specific counters rather than the generic ones. Follow this link for more information: https://msdn.microsoft.com/en-us/library/ff436045.aspx
Azure Guest OS Info: https://msdn.microsoft.com/en-us/library/ee924680.aspx
Thanks,
Patrick