Often, you can fix errors en masse. There are several ways. I recommend going to your Problems view, selecting one of the errors, and hitting Ctrl-1 (quick fix). It should offer you the chance to fix all the errors of the selected type, in all files.
You can also mouse over the error in the text editor and wait for a popup; it should say “fix 70 other errors of this type”. Doing it this way applies only to the specific file.