CefSharp.Wpf: Open csv, mailto and pdf with Process.Start(...) - wpf

Question

I need to handle different content types from f:///. My application renders offline websites in a WPF application. Everything is working except for links to other content files (csv, mailto and pdf).
If I register a CefCustomScheme for "mailto", then I get the ProcessRequestAsync and can run the Process.Start(...). However another blank window also popup.
If I then add a second CefCustomScheme for "file", then nothing happens. None of the ISchemeHandler ProcessRequestAsync methods are invoked.
I must be able to handle all requests, excluding *.html, in a separate handler
Essentially I just want to replicate the behavior of the MS Web-browser Control. There all I did was point to the entry page (index.htm), and everything loaded. Then if a user clicks any link, the control handled the action and started the correct process (content handler, i.e. Excel for Csv).
The code:
// Startup
var settings = new CefSettings();
settings.LogFile = #"c:\temp\ceflog.txt";
settings.LogSeverity = LogSeverity.Verbose;
settings.IgnoreCertificateErrors = true;
CefCustomScheme mailtoScheme = new CefCustomScheme();
mailtoScheme.SchemeName = "mailto";
mailtoScheme.SchemeHandlerFactory = new SchemeHandlerFactory();
CefCustomScheme filesScheme = new CefCustomScheme();
mailtoScheme.SchemeName = "file";
mailtoScheme.SchemeHandlerFactory = new SchemeHandlerFactory();
settings.RegisterScheme(mailtoScheme);
settings.RegisterScheme(filesScheme);
if (!Cef.Initialize(settings))
throw new InvalidOperationException("Failed to initialize the browser factory");
-- SchemeHandlerFactory
public class SchemeHandlerFactory : ISchemeHandlerFactory {
public ISchemeHandler Create() {
return new CustomSchemeHandler();
}
}
-- Handler
public class CustomSchemeHandler : ISchemeHandler {
private static readonly ILog _log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
public bool ProcessRequestAsync(IRequest request, ISchemeHandlerResponse response, OnRequestCompletedHandler requestCompletedCallback) {
_log.DebugFormat("Processing url: {0}", request.Dump());
var knownContentTypes = new[] {".csv", ".xsls", ".xlsx", ".pdf", ".txt"};
var ext=Path.GetExtension(request.Url);
if(knownContentTypes.Contains(ext)) {
_log.DebugFormat("Starting process for: {0}",request.Url);
Process.Start(request.Url);
return false;
}
return true;
}

Answer 1

The solution was to implement an IRequestHandler and use the OnBeforeResourceLoad event to check what content was requested. The ISchemeHandler is used for the "mailto" actions.
In my case I had to assign the request handler after the frame loaded. This allowed the web browser to render all content first.
Code sample GitHub example