That is impossible. I would suggest that you do not implement 'forgot password' functionality, but rather 'reset password'. You generate a new password, reset the password in Active Directory and send the new password to the user.
EDIT: Based on the information in your comment. First of all, it is a very bad idea to use an administrator account the way you use it now, with the account name and password as part of your code. You're running an ASP.NET site, so you should configure the application pool to run with this account.
Second, you should simply create a DirectoryEntry
with the correct path and reset the password. I'm not sure what your oEntry
is:
var userEntry = new DirectoryEntry(
"LDAP://CN=SomeUser,OU=Users,DC=yourdomain,DC=com");
using (userEntry)
{
userEntry.Invoke("SetPassword", new object[] { "NewPassword" });
userEntry.CommitChanges();
}