When coding in Visual Studio look out for the 
icon. It will often appear helping you to identify issues such as a missing namespace. If you see this icon appear you can press ‘Ctrl + .’ and it will bring up a helpful dialog with options to resolve the issue.
For Example:
In this situation pressing ‘Ctrl + .’ will bring up the option to include the ‘System.Text’ namespace or directly reference it preceding ‘StringBuilder’.
Hit the ‘Enter’ Key and it will take the first option in the list, automatically adding the namespace to your page.
