using System;
using System.DirectoryServices;
public class MyChangePasswordExample {
  public static void Main(string[] args) {
    DirectoryEntry myDirectoryEntry;

    myDirectoryEntry = new
    DirectoryEntry(@"WinNT://yourdirectoryserver/TheUsername,User");
  
    myDirectoryEntry.Invoke("setPassword", "NewPassword");
    myDirectoryEntry.CommitChanges();
  }
}