WinForms - Implement ChromiumWebBrowser.LoadError

amaitland · amaitland · commit 3cc3e642e9f8 · 2021-11-11T12:49:11.000+10:00
diff --git a/CefSharp.MinimalExample.WinForms/BrowserForm.cs b/CefSharp.MinimalExample.WinForms/BrowserForm.cs
@@ -35,6 +35,7 @@ public BrowserForm()
             browser.StatusMessage += OnBrowserStatusMessage;
             browser.TitleChanged += OnBrowserTitleChanged;
             browser.AddressChanged += OnBrowserAddressChanged;
+            browser.LoadError += OnBrowserLoadError;
 
             var version = string.Format("Chromium: {0}, CEF: {1}, CefSharp: {2}",
                Cef.ChromiumVersion, Cef.CefVersion, Cef.CefSharpVersion);
@@ -53,6 +54,34 @@ public BrowserForm()
             DisplayOutput(string.Format("{0}, {1}", version, environment));
         }
 
+        private async void OnBrowserLoadError(object sender, LoadErrorEventArgs e)
+        {
+            //Actions that trigger a download will raise an aborted error.
+            //Aborted is generally safe to ignore
+            if (e.ErrorCode == CefErrorCode.Aborted)
+            {
+                return;
+            }
+
+            //using LoadHtml/LoadUrl creates an additional history entry that
+            //prevents the back button from working correctly.
+            //Use Devools Page.SetDocumentContent to change the content
+            using (var client = browser.GetDevToolsClient())
+            {
+                var response = await client.Page.GetFrameTreeAsync();
+                var frames = response.FrameTree;
+                var mainFrame = frames.Frame;
+
+                var errorHtml = string.Format("<html><body><h2>Failed to load URL {0} with error {1} ({2}).</h2></body></html>",
+                                              e.FailedUrl, e.ErrorText, e.ErrorCode);
+
+                _ = client.Page.SetDocumentContentAsync(mainFrame.Id, errorHtml);
+
+                //AddressChanged isn't called for failed Urls so we need to manually update the Url TextBox
+                this.InvokeOnUiThreadIfRequired(() => urlTextBox.Text = e.FailedUrl);
+            }
+        }
+
         private void OnIsBrowserInitializedChanged(object sender, EventArgs e)
         {
             var b = ((ChromiumWebBrowser)sender);
