using System;
using System.IO;
namespace SearchFile
{
class Program
{
static void Main(string[] args)
{
DirectoryInfo directoryInfo = new DirectoryInfo(@"D:\"); //Put your folder path instead of 'D:\'
foreach (System.IO.FileInfo f in directoryInfo.GetFiles("*.*"))
{
string fileExtension = f.Name.Substring(f.Name.Length - 3, 3);
if(fileExtension == "txt" || fileExtension == "rtf" || fileExtension == "doc")
{
Console.WriteLine(f.Name);
}
}
}
}
}