Symptoms
What version of K2 is compatible with .Net Framework 4.6?
Diagnoses
All supportability and compatibility questions covered in K2 compatibility matrices which refelect information on supported configurations and versions of third party products against which K2 releases were tested. K 2 support matrices should be first thing to check whenever you plan updates of your K2 environments.
Please refer to links below to access product specific compatibility matrices:
http://help.k2.com/blackpearl/support-matrix
http://help.k2.com/smartforms/support-matrix
http://help.k2.com/connect/support-matrix
http://help.k2.com/appit/support-matrix
Resolution
Microsoft .NET 4.6 was released in July 2015 (K2 4.6.10 was released a month earlier, in June), and from K2 side official support for it has been added in K2 4.6.11.