Close the all browser windows(IE,google chrome,firefox) using C#

using System.Diagnostics;

Process[] AllProcesses = Process.GetProcesses();
            foreach (var process in AllProcesses)
            {
                if (process.MainWindowTitle != "")
                {
                    string s = process.ProcessName.ToLower();
                    if (s == "iexplore" || s == "iexplorer" || s == "chrome" || s == "firefox" )
                        process.Kill();
                }
            }