问题
I have tried to change the doctype from XHTML 1.0 to HTML5 doctype, by changing the doctype line in Site.Master.cs. However after the change HTML5 tags is still not recognized in Visual Studio 2010. Is there something more that I have to do to make it work?
回答1:
Right click on the tool bar at the top and enable the 'HTML Source Editing' tool bar.
You should then be able to select the target schema for validation from the drop down.
NOTE: Ensure you are viewing the aspx page, the drop down is greyed out otherwsie
回答2:
Here is an alternative solution that will work regardless of which type of page you're viewing:
Tools --> Options... --> Text Editor --> HTML --> Validation
Select the "Target:" from the dropdown that you'd like to use for validation.
来源：https://stackoverflow.com/questions/9191861/change-doctype-in-asp-net