using System;

public class Program

{

    public static void Main()

    {

        string fileName1 = "This is a file name with spaces (1).xls";

        Console.WriteLine(System.Net.WebUtility.UrlEncode(fileName1));

        string fileName2 = "This+is+a+file+name+with+plus+signs.xls";

        Console.WriteLine(System.Net.WebUtility.UrlEncode(fileName2));

    }

}