Open a URL in a new browser process

Question

I need to open a URL in a new browser process. I need to be notified when that browser process quits. The code I'm currently using is the following:

        Process browser = new Process();
        browser.EnableRaisingEvents = true;
        browser.StartInfo.Arguments = url;
        browser.StartInfo.FileName = "iexplore";

        browser.Exited += new EventHandler(browser_Exited);

        browser.Start();

Clearly, this won't due because the "FileName" is fixed to iexplore, not the user's default web browser. How do I figure out what the user's default web browser is?

I'm running on Vista->forward. Though XP would be nice to support if possible.

A bit more context: I've created a very small stand-alone web server that serves some files off a local disk. At the end of starting up the server I want to start the browser. Once the user is done and closes the browser I'd like to quit the web server. The above code works perfectly, other than using only IE.

Thanks in advance!

Answer 1

The way to determine the default browser is explained in this blog post:

http://ryanfarley.com/blog/archive/2004/05/16/649.aspx

From the blog post above:

private string getDefaultBrowser()
{
    string browser = string.Empty;
    RegistryKey key = null;
    try
    {
        key = Registry.ClassesRoot.OpenSubKey(@"HTTP\shell\open\command", false);

        //trim off quotes
        browser = key.GetValue(null).ToString().ToLower().Replace("\"", "");
        if (!browser.EndsWith("exe"))
        {
            //get rid of everything after the ".exe"
            browser = browser.Substring(0, browser.LastIndexOf(".exe")+4);
        }
    }
    finally
    {
        if (key != null) key.Close();
    }
    return browser;
}

Answer 2

Hi, Ok, I think I might have found it - IApplicationAssociationRegistration::QueryCurrentDefault [1]. According to the docs this is what is used by ShellExecute. I'll post code when I get it to work, but I'd be interested if others think this is the right thing to use (BTW, I'm Vista or greater for OS level).

[1]: http://msdn.microsoft.com/en-us/library/bb776336(VS.85).aspx QueryCurrentDefault

Answer 3

If you pass a path of the known file type to the (file) explorer application, it will 'do the right thing', e.g.

 Process.Start("explorer.exe", @"\\path.to\filename.pdf");

and open the file in the PDF reader.

But if you try the same thing with a URL, e.g.

Process.Start("explorer.exe", @"http://www.stackoverflow.com/");

it fires up IE (which isn't the default browser on my machine).

I know doesn't answer the question, but I thought it was an interesting sidenote.

Answer 4

Ok. Been away on the conference circuit for a week, now getting back to this. I can do this with C++ now - and it even seems to behave properly! My attempts to translate this into C# (or .NET) have all failed however (Post On Question).

Here is the C++ code for others that stumble on this question:

#include "stdafx.h"
#include <iostream>
#include <shobjidl.h>
#define _ATL_CSTRING_EXPLICIT_CONSTRUCTORS      // some CString constructors will be explicit

#include <atlbase.h>
#include <atlstr.h>
#include <AtlDef.h>
#include <AtlConv.h>

using namespace std;
using namespace ATL;

int _tmain(int argc, _TCHAR* argv[])
{
    HRESULT hr = CoInitialize(NULL);
    if (!SUCCEEDED(hr)) {
     cout << "Failed to init COM instance" << endl;
     cout << hr << endl;
    }

    IApplicationAssociationRegistration *pAAR;
    hr = CoCreateInstance(CLSID_ApplicationAssociationRegistration,
     NULL, CLSCTX_INPROC, __uuidof(IApplicationAssociationRegistration),
     (void**) &pAAR);
    if (!SUCCEEDED(hr))
    {
     cout << "Failed to create COM object" << endl;
     cout << hr << endl;
     return 0;
    }

    LPWSTR progID;
    //wchar_t *ttype = ".txt";
    hr = pAAR->QueryCurrentDefault (L".txt", AT_FILEEXTENSION, AL_EFFECTIVE, &progID);
    if (!SUCCEEDED(hr)) {
     cout << "Failed to query default for .txt" << endl;
     cout << hr << endl;
    }
    CW2A myprogID (progID);
    cout << "Result is: " << static_cast<const char*>(myprogID) << endl;

    /// Now for http

    hr = pAAR->QueryCurrentDefault (L"http", AT_URLPROTOCOL, AL_EFFECTIVE, &progID);
    if (!SUCCEEDED(hr)) {
     cout << "Failed to query default for http" << endl;
     cout << hr << endl;
    }
    CW2A myprogID1 (progID);
    cout << "Result is: " << static_cast<const char*>(myprogID1) << endl;

    return 0;
}

I will post the C# code when I finally get it working!

Answer 5

Short answer, you can't.

If the default browser is, say, Firefox, and the user already has a Firefox instance running, it will just be opened in another window or tab of the same firefox.exe process, and even after they close your page, the process won't exit until they close every window and tab. In this case, you would receive notification of the process exiting as soon as you started it, due to the temporary firefox.exe proc that would marshal the URL to the current process. (Assuming that's how Firefox's single instance management works).

Answer 6

Ok. I now have working C# code to do what I want. This will return the "command line" you should run to load the current default browser:

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Linq;
using System.Text;

namespace testDefaultBrowser
{
    public enum ASSOCIATIONLEVEL
    {
        AL_MACHINE,
        AL_EFFECTIVE,
        AL_USER,
    };

    public enum ASSOCIATIONTYPE
    {
        AT_FILEEXTENSION,
        AT_URLPROTOCOL,
        AT_STARTMENUCLIENT,
        AT_MIMETYPE,
    };

    [Guid("4e530b0a-e611-4c77-a3ac-9031d022281b"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IApplicationAssociationRegistration
    {
        void QueryCurrentDefault([In, MarshalAs(UnmanagedType.LPWStr)] string pszQuery,
        [In, MarshalAs(UnmanagedType.I4)] ASSOCIATIONTYPE atQueryType,
        [In, MarshalAs(UnmanagedType.I4)] ASSOCIATIONLEVEL alQueryLevel,
        [Out, MarshalAs(UnmanagedType.LPWStr)] out string ppszAssociation);

        void QueryAppIsDefault(
            [In, MarshalAs(UnmanagedType.LPWStr)] string pszQuery,
            [In] ASSOCIATIONTYPE atQueryType,
            [In] ASSOCIATIONLEVEL alQueryLevel,
            [In, MarshalAs(UnmanagedType.LPWStr)] string pszAppRegistryName,
            [Out] out bool pfDefault);

        void QueryAppIsDefaultAll(
            [In] ASSOCIATIONLEVEL alQueryLevel,
            [In, MarshalAs(UnmanagedType.LPWStr)] string pszAppRegistryName,
            [Out] out bool pfDefault);

        void SetAppAsDefault(
            [In, MarshalAs(UnmanagedType.LPWStr)] string pszAppRegistryName,
            [In, MarshalAs(UnmanagedType.LPWStr)] string pszSet,
            [In] ASSOCIATIONTYPE atSetType);

        void SetAppAsDefaultAll(
            [In, MarshalAs(UnmanagedType.LPWStr)] string pszAppRegistryName);

        void ClearUserAssociations();
    }

    [ComImport, Guid("591209c7-767b-42b2-9fba-44ee4615f2c7")]//
    class ApplicationAssociationRegistration
    {
    }

    class Program
    {
        static void Main(string[] args)
        {
            IApplicationAssociationRegistration reg = 
                (IApplicationAssociationRegistration) new ApplicationAssociationRegistration();

            string progID;
            reg.QueryCurrentDefault(".txt",
                ASSOCIATIONTYPE.AT_FILEEXTENSION,
                ASSOCIATIONLEVEL.AL_EFFECTIVE,
                out progID);
            Console.WriteLine(progID);

            reg.QueryCurrentDefault("http",
                ASSOCIATIONTYPE.AT_URLPROTOCOL,
                ASSOCIATIONLEVEL.AL_EFFECTIVE,
                out progID);
            Console.WriteLine(progID);
        }
    }
}

Whew! Thanks everyone for help in pushing me towards the right answer!