Directory Services Com Exception Logon failure: unknown user name or bad password

Question

I am trying to query LDAP server for a valid credential (username and password). The problem is eventhough the credential itself is registered in the server it doesn't get authenticated. If i put old ldapPath it works fine. The code is running on visual studio development server on my local machine (Not IIS). Whenever i run this i get "Directory Services Com Exception. Logon failure: unknown user name or bad password.".

const string ldapPath="LDAP:\\newDomain"; //please note this is just an example
public override bool ValidateUser(string username, string password)
    {

            DirectoryEntry directoryEntry = new DirectoryEntry(ldapPath, username, password, AuthenticationTypes.ServerBind);


            DirectorySearcher directorySearcher = new DirectorySearcher(directoryEntry)
            {
                SearchScope = SearchScope.Subtree,
                Filter = "uid="+username
            };

            try
            {
                using(HostingEnvironment.Impersonate())
                {
                    SearchResult resultEmployee = directorySearcher.FindOne();
                    return resultEmployee.Properties["uid"].Count == 1;
                }

            }
            catch (DirectoryServicesCOMException)
            {
                return false;
            }       

    }