using System;

using System.IO;

using System.Text.RegularExpressions;

​

// R.Wilson @Nasa 11/2019

public class Program

{

    public static void Main()

    {

        foreach(var junk in new String[] {"A2","A 2.txt","A 2!@#$%^&*_()-+={}[]~`,.<>:\";'\\/?"}) 

        {

            string name = "DRONE_Cert" + junk;

            string ext = ".txt?q=100"; // null

            Console.WriteLine("ORIGINAL: " + name + ext);           

            Console.WriteLine("TEST-1  : " + MakeValidFileName(name,ext));

            Console.WriteLine("TEST-2  : " + MakeValidFileName2(name,ext));

            Console.WriteLine("-----------------------------------------");

        }

    }

    // Returns a filename with query string and special characters removed.

    // Note that invalid = @"[\W]"  seems to work just as well

    public static string MakeValidFileName2(string name, string ext) 

    {

           var invalid = @"[\W*" + new string(Path.GetInvalidFileNameChars()) + "*]";

            name = (name??"noname").Split('.')[0];

            name = Regex.Replace(name, invalid,"");

            ext = (ext??"").Split('?','#')[0]; 

            ext = Regex.Replace(ext, invalid, "");

            if (!String.IsNullOrWhiteSpace(ext)) ext = "." + ext;

            return name + ext;

    }

    public static string MakeValidFileName(string fileName, string extension)

    {

        try {

            fileName = fileName.Replace(extension, string.Empty);

​

            char[] invalidChars = Path.GetInvalidFileNameChars();

​

            foreach (char c in invalidChars)

            {

                //remove invalid chars 

                fileName = fileName.Replace(c.ToString(), string.Empty);

            }

​

            //remove excess dots as well

            fileName = fileName.Replace(".", string.Empty);

            fileName = fileName.Replace(",", string.Empty);

            fileName = fileName.Replace("/", string.Empty);

            fileName = fileName.Replace("\\", string.Empty);

            fileName = fileName.Replace("<", string.Empty);

            fileName = fileName.Replace(">", string.Empty);

            fileName = fileName.Replace(":", string.Empty);

            fileName = fileName.Replace("*", string.Empty);

            fileName = fileName.Replace("|", string.Empty);

            fileName = fileName.Replace("\"", string.Empty);

​

            extension = extension.Replace(".", string.Empty); //Added to ensure extra period not in extensions as well

            //fileName = TruncateFileName(fileName, 200 - (extension.Length + 1)); //200 characters total including the extension and .

​

            return fileName + "." + extension;

        }

        catch 

        {

            return "error";

        }

    }

}