How to find default web browser using C#?

Question

Is there a way I can find out the name of my default web browser using C#? (Firefox, Google Chrome, etc..)

Can you please show me with an example?

Answer 1

Here's something I cooked up from combining the responses here with correct protocol handling:

/// 

///     Opens a local file or url in the default web browser.
///     Can be used both for opening urls, or html readme docs.
/// 
/// Path of the local file or url
/// False if the default browser could not be opened.
public static Boolean OpenInDefaultBrowser(String pathOrUrl)
{
    // Trim any surrounding quotes and spaces.
    pathOrUrl = pathOrUrl.Trim().Trim('"').Trim();
    // Default protocol to "http"
    String protocol = Uri.UriSchemeHttp;
    // Correct the protocol to that in the actual url
    if (Regex.IsMatch(pathOrUrl, "^[a-z]+" + Regex.Escape(Uri.SchemeDelimiter), RegexOptions.IgnoreCase))
    {
        Int32 schemeEnd = pathOrUrl.IndexOf(Uri.SchemeDelimiter, StringComparison.Ordinal);
        if (schemeEnd > -1)
            protocol = pathOrUrl.Substring(0, schemeEnd).ToLowerInvariant();
    }
    // Surround with quotes
    pathOrUrl = "\"" + pathOrUrl + "\"";
    Object fetchedVal;
    String defBrowser = null;
    // Look up user choice translation of protocol to program id
    using (RegistryKey userDefBrowserKey = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\Shell\Associations\UrlAssociations\" + protocol + @"\UserChoice"))
        if (userDefBrowserKey != null && (fetchedVal = userDefBrowserKey.GetValue("Progid")) != null)
            // Programs are looked up the same way as protocols in the later code, so we just overwrite the protocol variable.
            protocol = fetchedVal as String;
    // Look up protocol (or programId from UserChoice) in the registry, in priority order.
    // Current User registry
    using (RegistryKey defBrowserKey = Registry.CurrentUser.OpenSubKey(@"SOFTWARE\Classes\" + protocol + @"\shell\open\command"))
        if (defBrowserKey != null && (fetchedVal = defBrowserKey.GetValue(null)) != null)
            defBrowser = fetchedVal as String;
    // Local Machine registry
    if (defBrowser == null)
        using (RegistryKey defBrowserKey = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Classes\" + protocol + @"\shell\open\command"))
            if (defBrowserKey != null && (fetchedVal = defBrowserKey.GetValue(null)) != null)
                defBrowser = fetchedVal as String;
    // Root registry
    if (defBrowser == null)
        using (RegistryKey defBrowserKey = Registry.ClassesRoot.OpenSubKey(protocol + @"\shell\open\command"))
            if (defBrowserKey != null && (fetchedVal = defBrowserKey.GetValue(null)) != null)
                defBrowser = fetchedVal as String;
    // Nothing found. Return.
    if (String.IsNullOrEmpty(defBrowser))
        return false;
    String defBrowserProcess;
    // Parse browser parameters. This code first assembles the full command line, and then splits it into the program and its parameters.
    Boolean hasArg = false;
    if (defBrowser.Contains("%1"))
    {
        // If url in the command line is surrounded by quotes, ignore those; our url already has quotes.
        if (defBrowser.Contains("\"%1\""))
            defBrowser = defBrowser.Replace("\"%1\"", pathOrUrl);
        else
            defBrowser = defBrowser.Replace("%1", pathOrUrl);
        hasArg = true;
    }
    Int32 spIndex;
    if (defBrowser[0] == '"')
        defBrowserProcess = defBrowser.Substring(0, defBrowser.IndexOf('"', 1) + 2).Trim();
    else if ((spIndex = defBrowser.IndexOf(" ", StringComparison.Ordinal)) > -1)
        defBrowserProcess = defBrowser.Substring(0, spIndex).Trim();
    else
        defBrowserProcess = defBrowser;

    String defBrowserArgs = defBrowser.Substring(defBrowserProcess.Length).TrimStart();
    // Not sure if this is possible / allowed, but better support it anyway.
    if (!hasArg)
    {
        if (defBrowserArgs.Length > 0)
            defBrowserArgs += " ";
        defBrowserArgs += pathOrUrl;
    }
    // Run the process.
    defBrowserProcess = defBrowserProcess.Trim('"');
    if (!File.Exists(defBrowserProcess))
        return false;
    ProcessStartInfo psi = new ProcessStartInfo(defBrowserProcess, defBrowserArgs);
    psi.WorkingDirectory = Path.GetDirectoryName(defBrowserProcess);
    Process.Start(psi);
    return true;
}