Files you delete in Visual Studio go to Windows recycle bin. Unless you cleared it, your files should still be there. Just restore them and than add them to your project as existing items. You can also drag and drop them through Solution Explorer.
EDIT:
You can also click the “Show All Files” button in solution explorer.
The file will appear there, grayed out (if it was only removed from your project – not your disk drive). Then you can right-click it, and add it back to the ptoject. If it’s not there try the first approach.