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Asked: 2026-06-12T03:39:51+00:00

Well, for example I have some simple console application. My purpose is to generate

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Well, for example I have some simple console application. My purpose is to generate some report and represent it to the user in some external application such as notepad or a web browser.

class Program
    {
        [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
        public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

        [DllImport("User32.dll")]
        public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);

        static void Main()
        {
            OpenNotepadAndInputTextInIt("Message in notepad");
            OpenHtmlFileInBrowser(@"c:\temp\test.html");
        }

        private static string GetDefaultBrowserPath()
        {
            string key = @"HTTP\shell\open\command";
            using(RegistryKey registrykey = Registry.ClassesRoot.OpenSubKey(key, false))
            {
                return ((string)registrykey.GetValue(null, null)).Split('"')[1];
            }
        }

        private static void OpenHtmlFileInBrowser(string localHtmlFilePathOnMyPc)
        {
            Process browser = Process.Start(new ProcessStartInfo(GetDefaultBrowserPath(), string.Format("file:///{0}", localHtmlFilePathOnMyPc)));
            browser.WaitForInputIdle();

        }

        private static void OpenNotepadAndInputTextInIt(string textToInputInNotepad)
        {
            Process notepad = Process.Start(new ProcessStartInfo("notepad.exe"));
            notepad.WaitForInputIdle();
            if(notepad != null)
            {
                IntPtr child = FindWindowEx(notepad.MainWindowHandle, new IntPtr(0), "Edit", null);
                SendMessage(child, 0x000C, 0, textToInputInNotepad);
            }
        }
    }

This solution works fine, But as you can see I have two methods; GetDefaultBrowserPath() and GetDefaultBrowserPath(string localHtmlFilePathInMyPc). The first one passes message string directly to notepad window, but the second one needs to create a file, some html page, and than pass this html file as parameter for the web browser. This is kind of a slow solution. I want to generate an html string report and pass it directly to a web browser without creating intermediate html files.

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1 Answer

  1. Editorial Team

    If you want to open an external browser window (rather than integrating one into your application) in the system’s default browser application I think the only way is going via a data URI:

    data:text/html,<html><title>Hello</title><p>This%20is%20a%20test

    Pass this as the URI into the browser. However, I wouldn’t really advise doing this. It’s unexpected for the user and there isn’t really a disadvantage in generating a temporary file to be displayed, is there? In addition, you might start hitting restrictions on the URI length pretty quickly.

    Incidentally, your current way of opening a file in the browser is way more complicated than required. Shell execution does the right thing on its own, no need to retrieve the browser’s path from the registry manually:

    Process.Start("file:///the/path/here")
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