I have one web site develop using vs2008 version and I trying to upgrade to vs2015 community version. When I change from .Net framework 2.0 to 4.0. Below error appear:
Error BC30451 'ScriptManager' is not declared. It may be inaccessible due to its protection level
I have a script manger with ID='ScriptManager1'. But when I goto code behind, I couldn't found this component.
How was caused this happen? I have tried many ways but still cannot solved. Help.. Thanks.