Exposing this might be nice of course. :)

Author: perlun

CefSharp/LoadCompletedEventArgs.h

@@ -15,6 +15,7 @@ namespace CefSharp
             : _url(url), _isMainFrame(isMainFrame) {}
 
         property String^ Url { String^ get() { return _url; } }
+        property bool IsMainFrame { bool get() { return _isMainFrame; }
     };
 
     public delegate void LoadCompletedEventHandler(Object^ sender, LoadCompletedEventArgs^ url);

CefSharp/LoadStartedEventArgs.h

@@ -15,6 +15,7 @@ namespace CefSharp
             : _url(url), _isMainFrame(isMainFrame) {}
 
         property String^ Url { String^ get() { return _url; } }
+        property bool IsMainFrame { bool get() { return _isMainFrame; }
     };
 
     public delegate void LoadStartedEventHandler(Object^ sender, LoadStartedEventArgs^ url);