Index: tools/clang-format-vs/ClangFormat/ClangFormatPackage.cs
===================================================================
--- tools/clang-format-vs/ClangFormat/ClangFormatPackage.cs
+++ tools/clang-format-vs/ClangFormat/ClangFormatPackage.cs
@@ -84,8 +84,13 @@
                 // We're not in a text view.
                 return;
             string text = view.TextBuffer.CurrentSnapshot.GetText();
-            int start = view.Selection.Start.Position.GetContainingLine().Start.Position;
-            int end = view.Selection.End.Position.GetContainingLine().End.Position;
+            int start = 0;
+            int end = text.Length;
+            if (!view.Selection.IsEmpty)
+            {
+                start = view.Selection.Start.Position.GetContainingLine().Start.Position;
+                end = view.Selection.End.Position.GetContainingLine().End.Position;
+            }
             int length = end - start;
             // clang-format doesn't support formatting a range that starts at the end
             // of the file.