Compress huge folders by individual in directory? Using 7z.exe

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C#4.0

console

static void Main(string[] args)
       {
           var fileDirPath = new DirectoryInfo(@"C:\7compressNigol");
           FileInfo[] Files = fileDirPath.GetFiles("*.*");
           //var prefferedPath = @"C:\7compressNigol\123.zip";
           List<string> filesToZip = new List<string>();
           foreach (FileInfo file in Files)
           {
               ProcessStartInfo p = new ProcessStartInfo();
               p.FileName = @"C:\7compressNigol\7z.exe";
               //p.Arguments = "a /d \"" + prefferedPath + "\" \"" + fileDirPath + "\"";
               p.Arguments = "a \"" + file + "\" \"";
               p.WindowStyle = ProcessWindowStyle.Hidden;
               Process x = Process.Start(p);
               x.WaitForExit();
               return;
           }
       }

What I have tried:

I'm using 7z.exe to compress huge folders that contain in a directory, so how to edit my code, I want it compress each folder with same name?