How to Authenticate LDAP in .NET

Question

I would like to authenticate username and passwords for my application on a windows operating system with any directory service. For example it could be microsoft active di

Answer 1

I'm not sure I entirely understand the question, but in some situations I've found it easy to authenticate a user by simply doing a search for their account and using their credentials as the username and password.

A successful query means everything provided was correct, not finding the account means something was wrong.

//use the users credentials for the query
DirectoryEntry root = new DirectoryEntry(
    "LDAP://dc=domain,dc=com", 
    loginUser, 
    loginPassword
    );

//query for the username provided
DirectorySearcher searcher = new DirectorySearcher(
    root, 
    "(sAMAccountName=" + loginUser + ")"
    );    

//a success means the password was right
bool success = false; 
try {
    searcher.FindOne();
    success = true;
}
catch {
    success = false;
}

Probably not "best practice", but might get around your issue you are having...