field_merge: Example code of Early Access iText(how to fill PDF form with iTextSharp)

using System;
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.IO;
public class field_merge
{
    
    private static void  usage()
    {
        
        System.Console.Out.WriteLine("Field merging and flattening");
        System.Console.Out.WriteLine("usage: field_merge [-f] infile_pdf outfile_pdf [[name1=value1][namex=valuex]]");
        System.Console.Out.WriteLine("    -f - flatten the fields");
    }
    

    [STAThread]
    public static void  Main(string[] args)
    {
        if (args.Length < 2)
        {
            usage();
            return ;
        }
        int idx = 0;
        if (args[0].Equals("-f"))
            ++idx;
        if (args.Length - idx < 2)
        {
            usage();
            return ;
        }
        string in_pdf = args[idx];
        string out_pdf = args[idx + 1];
        try
        {
            PdfReader reader = new PdfReader(in_pdf);
            PdfStamper stamp = new PdfStamper(reader, new FileStream(out_pdf, FileMode.Create));
            AcroFields form = stamp.AcroFields;
            for (int k = idx + 2; k < args.Length; ++k)
            {
                string t = args[k];
                int x = t.IndexOf((System.Char) '=');
                if (x > 0)
                {
                    string field = t.Substring(0, (x) - (0));
                    string value_Renamed = t.Substring(x + 1);
                    form.SetField(field, value_Renamed);
                }
            }
            if (idx > 0)
                stamp.FormFlattening=(true);
            stamp.Close();
            System.Console.Out.WriteLine("Done.");
        }
        catch (System.Exception e)
        {
            System.Console.Error.WriteLine(e.Message);
        }
    }
}