c#

gistfile1.cs

using System;
using System.IO;
 
namespace Rename
{
  class MainClass
  {
    static DirectoryInfo d = new DirectoryInfo(Directory.GetCurrentDirectory());
 
    static FileInfo[] Files = d.GetFiles("*.png");
 
    public static void Main(string[] args)
    {
      Console.WriteLine(Directory.GetCurrentDirectory());
 
      foreach (var a in Files)
      {
        Console.WriteLine(a.Name);
        if (a.Name.Contains("@"))
        {
          var index = a.FullName.LastIndexOf('.');
          var path = a.FullName.Substring(0, index - 3).TrimEnd() + ".png";
             
          try
          {
            File.Move(a.FullName, path);
          }
          catch
          {

            File.Delete(path);
            File.Move(a.FullName, path);
          }
        }
        
      }

      if(args.Length != 0)
      {
        Files = d.GetFiles("*.png");
        foreach(var a in Files)
        {
          File.Move(a.FullName, args[0]+a.FullName);
        }
      }
    }
  }
}