c# - Silent installation

Question

I am writing a InstallerClass using C# as a custom action for my installer, and I can successfully run an external exe (installation) using the InstallerClass, but when I try to use /quiet in the InstallerClass, it does not install the exe. But I can successfully install this in silent mode using /quiet in the command prompt.

Is there any reason for this or otherwise how to install in silent mode using C#?

Following is the code I use within the Commit method (overriden):

Process p = new Process();
p.StartInfo.UseShellExecute = false;
p.StartInfo.FileName = pathExternalInstaller;
p.StartInfo.Arguments = "/quiet";
p.Start();

Answer 1

Here is what I use to do a quiet Install and Uninstall:

    public static bool RunInstallMSI(string sMSIPath)
    {
        try
        {
            Console.WriteLine("Starting to install application");
            Process process = new Process();
            process.StartInfo.FileName = "msiexec.exe";
            process.StartInfo.Arguments = string.Format(" /qb /i "{0}" ALLUSERS=1", sMSIPath);      
            process.Start();
            process.WaitForExit();
            Console.WriteLine("Application installed successfully!");
            return true; //Return True if process ended successfully
        }
        catch
        {
            Console.WriteLine("There was a problem installing the application!");
            return false;  //Return False if process ended unsuccessfully
        }
    }

    public static bool RunUninstallMSI(string guid)
    {
        try
        {
            Console.WriteLine("Starting to uninstall application");
            ProcessStartInfo startInfo = new ProcessStartInfo("cmd.exe", string.Format("/c start /MIN /wait msiexec.exe /x {0} /quiet", guid));
            startInfo.WindowStyle = ProcessWindowStyle.Hidden;
            Process process = Process.Start(startInfo);
            process.WaitForExit();
            Console.WriteLine("Application uninstalled successfully!");
            return true; //Return True if process ended successfully
        }
        catch
        {
            Console.WriteLine("There was a problem uninstalling the application!");
            return false; //Return False if process ended unsuccessfully
        }
    }