I am using VS Community 2015 and I am getting a ton of these on some of the pages in the error list in my project. They are not valid errors. If I open the particular page in the source window, they are no longer reported. I can compile and run the project. It can make it very difficult to find real errors.
I can not find any info about this error when it is incorrectly reported.
Error BC30451 'GridView1' is not declared. It may be inaccessible due to its protection level. WebSite1(1) C:\...\...\Documents\Visual Studio 2015\WebSites\WebSite1\EditProjects.aspx.vb 15