Process.Start(url) in a loop not launching every instance

I have a need to launch multiple browser instances / tabs in succession but using Process.Start(url) I am finding that not every URL is launched.

    for (int i = 0; i < n; i++)
    {
        var p = Process.Start("http://localhost/#" + i.ToString());
    }

For any value n > 1 I find that only the last URL is opened in the browser (I'm testing with IE as the default browser). If I add a Thread.Sleep(1000) after Process.Start then I see a variety of behavior: sometimes all n are created; sometimes a subset.

The following does work a开发者_C百科s expected, but assumes IE (would rather use the default browser) and launches n browser instances rather than n tabs:

    for (int i = 0; i < n; i++)
    {
        var p = Process.Start("iexplore.exe", "http://localhost/#" + i.ToString());
    }

I would prefer to get it working with the default browser behavior, but need it to be deterministic.

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Seems to be a windows explorer bug. You could try to find to common browser executables and use them if present, if no match is found you can fall back to your default method.

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Also see Open multiple-tabs in IE9 using Process (possible duplicate)

We are working on exactly this issue for IE9. This seems to work.

bool isLaunched = false;
foreach (string url in urls)
{
    try
    {
        if (!isLaunched)
        {
            Process p = new Process();
            p.StartInfo.FileName = browser;
            p.StartInfo.Arguments = url;
            p.Start();
            Thread.Sleep(1000);
            isLaunched = true;
        }
        else
        {
            Process.Start(url);
        }
    }
    catch (Exception ex)
    {
// something

    }
}

In my experience p.WaitForIdle does not work. Also, there are differences in behavior if a browser instance is already open on the machine. Calling iexplore actually passes the url to the open instance and exits your called process.

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I'm completely winging this one, but here it goes. Derived from @tofutim's answer. Basically, use locking and monitor the Process state with a Timer. This of course is highly dependent on being able to determine if the process has successfully started, which is being tested with

if (p.HasExited == false && p.Id != 0){ }

The full solution:

bool isLaunching = false;
object launchingLock = new object();
Process p = null;

Timer timer = new Timer(new TimerCallback((state) =>
{
    lock (launchingLock)
    {
        if (isLaunching)
        {
            if (p != null && p.HasExited == false && p.Id != 0)
            {
                // Success! 
                isLaunching = false;
                Monitor.PulseAll(launchingLock);
            }
            else if(p != null && p.HasExited)
            {
                // Some sort of failure code/notification?
                // We still want to pulse though, otherwise thread will be forever kept waiting
                isLaunching = false;
                Monitor.PulseAll(launchingLock);
            }
        }
    }
}));

timer.Change(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));

foreach (string url in urls)
{
    try
    {
        lock (launchingLock)
        {
            isLaunching = true;
            p = new Process();
            p.StartInfo.FileName = browser;
            p.StartInfo.Arguments = url;
            p.Start();

            // Wait until the process has finished starting before moving on
            Monitor.Wait(launchingLock);
        }
    }
    catch (Exception ex)
    {
        // something
    }
}

timer.Dispose();

---

Ended up with the following, still not ideal (launches multiple browser windows), incorporating the command-line arg parsing solution Split string containing command-line parameters into string[] in C#

const int n = 3;
static void Main(string[] args)
{
    for (int i = 0; i < n; i++)
    {
        var start = GetDefaultBrowserStartInfo("http");
        start.Arguments += string.Format(" http://localhost/#{0}", i);

        var p = Process.Start(start);
    }
}

static ProcessStartInfo GetDefaultBrowserStartInfo(string scheme)
{
    string command = null;
    using (var key = Registry.ClassesRoot.OpenSubKey(string.Format(@"{0}\shell\open\command", scheme)))
    {
        command = (string)key.GetValue("");
    }

    string[] parsed = CommandLineToArgs(command);
    return new ProcessStartInfo
    {
        FileName = parsed[0],
        Arguments = string.Join(" ", parsed.Skip(1).ToArray()),
    };
}

[DllImport("shell32.dll", SetLastError = true)]
static extern IntPtr CommandLineToArgvW(
    [MarshalAs(UnmanagedType.LPWStr)] string lpCmdLine, out int pNumArgs);

static string[] CommandLineToArgs(string commandLine)
{
    int argc;
    var argv = CommandLineToArgvW(commandLine, out argc);
    if (argv == IntPtr.Zero)
        throw new System.ComponentModel.Win32Exception();
    try
    {
        var args = new string[argc];
        for (var i = 0; i < args.Length; i++)
        {
            var p = Marshal.ReadIntPtr(argv, i * IntPtr.Size);
            args[i] = Marshal.PtrToStringUni(p);
        }

        return args;
    }
    finally
    {
        Marshal.FreeHGlobal(argv);
    }
}

}