C# Disable JavaScript error in WebBrowser control

When using the WebBrowser control and loading a html page it is possible that a message appears that there is a javascript error. This is especially the case if the webpage has been saved from the web and is then displayed on a computer which is offline. Unfortunately there is no property on the browser control which can be used to suppress this kind of error. It is however possible to inject a script tag in the header of an loaded html-file which does catch all errors. Therefore no message will be displayed. You can use the following snippet:

        private void SuppressScriptErrors(WebBrowser wb) {
            HTMLDocument doc = wb.Document as HTMLDocument;

            if (doc != null) {
                IHTMLScriptElement scriptErrorSuppressed = (IHTMLScriptElement)doc.createElement("SCRIPT");
                scriptErrorSuppressed.type = "text/javascript";
                scriptErrorSuppressed.text =
                    @"function noError() { 
                                                return true; 
                                            }

                                            window.onerror = noError;";
                IHTMLElementCollection nodes = doc.getElementsByTagName("head");

                foreach (IHTMLElement node in nodes) {
                    HTMLHeadElementClass head = (HTMLHeadElementClass)node;
                    head.appendChild((IHTMLDOMNode)scriptErrorSuppressed);
                }
            }
        }

The injection does also work if a file like a word-document or a pdf-file is opened within the webbrowser. There won’t be an error because it is no html-file.

You might get an error (Interop type xxx cannot be embedded. Use the applicable interface instead) which can be resolved with a reference to “Microsoft HTML Object Library (MSHTML) choosing EmbedInteropTypes = False in the properties