When converting a website to a web app, the designer creates the code
protected global::System.Web.UI.WebControls.LinqDataSource
and I get the error
namespace name 'LinqDataSource' does not exist in the namespace 'System.Web.UI.WebControls'
when I try to compile.
I tried creating a new project, making sure LinqDataSource was working by adding it from the toolbox to a webpage.
After copying my existing project into the solution as a folder it failed, turns out it doesn't like the bin folder from my previous project in a subfolder of the new project.