invoking MSIEXEC within a Process fails

Question

I have the following piece of service code to install a group of MSI files copied to a given directory:

    private void InvokeInstallersIn(string path)
    {
        var di = new DirectoryInfo(path);
        foreach (FileInfo fileInfo in di.GetFiles("*.msi"))
        {
            try
            {
                ProcessStartInfo start = new ProcessStartInfo();
                start.FileName = @"msiexec.exe"; // Specify exe name.
                start.UseShellExecute = true;
                start.RedirectStandardOutput = false;
                start.WorkingDirectory = path;
                var arguments = @"/I /l*v install.log /qn " + 
                    fileInfo.Name + " REINSTALL=All REINSTALLMODE=amus";
                start.Arguments = arguments;
                Logger.Info("Process: msiexec.exe {0}", arguments);
                Process process = Process.Start(start);
                process.WaitForExit(30000);
            }
            catch (System.Exception e)
            {
                Logger.ErrorEx(e, "Error installing '{0}'", fileInfo.Name);
            }
        }
    }

Whenever it invokes msiexec it ends up displaying the usage dialog instead of performing the installation.

Update

I can install the MSI via windows explorer, but cannot from the command line at all. In addition I cannot change the file privileges on the msi file, and the installer displays the "This file does not have a valid digital signature..." warning when I invoke via explorer. (I'd copied this file to a share on my own machine and am accessing it in explorer via \localhost\MyShare). Perhaps the question is now - how do I choose to override this warning from the command line.

Any clues as to where I'm going wrong?

Answer 1

The MSI name belongs immediately after /I, i.e.

string.format(@"/I {0} /l*v install.log /qnx REINSTALL=All REINSTALLMODE=amus", fileInfo.Name);

As for the warning, AFAIK you can't override it, but it will go away if you digitally sign the MSI with a valid certificate.