Recursively Search Directory for a File

System.Collections.ArrayList files = new System.Collections.ArrayList();
DirSearch(@"C:",ref files);
//Method to Search Directory for specified file Type.Paste it outside the function
public void DirSearch(string sDir,ref System.Collections.ArrayList files)
{
try
{
foreach (string d in System.IO.Directory.GetDirectories(sDir))
{
foreach (string f in System.IO.Directory.GetFiles(d, "*.txt"))
{
files.Add(f);
}
DirSearch(d,ref files);
}
}
catch (System.Exception excpt)
{
Console.WriteLine(excpt.Message);
}
}