LDAP Authentication pass credentials

LDAP Authentication pass credentials

I need to pass LDAP credentials to a web-service to authenticate in C#.
I've got everything setup to get the user using DirectoryEntry, however,
for obvious reasons I can't get the password.
I authenticate to a third-party web service in C# by passing the
username/password like:
j_username=me%40domain.com&j_password=mypassword%21
I know getting the LDAP password is impossible but is there a better way
to go about what I'm doing?