C# Retrieve Get Directory User Attributes

UserPrincipal user = UserPrincipal.FindByIdentity(GetPrincipalContext(), IdentityType.SamAccountName, alias);
if (user != null)
{   
    DirectoryEntry directoryEntry = (user.GetUnderlyingObject() as DirectoryEntry);
    DirectorySearcher adSearch = new DirectorySearcher(directoryEntry);   
    adSearch.SearchScope = SearchScope.Subtree;
    adSearch.Filter = "(&(ObjectClass=user)(sAMAccountName=" + alias + "))";
    SearchResult sResult = adSearch.FindOne();

    if (sResult.Properties.Contains(attribute))
        propertyValue = sResult.Properties[attribute][0].ToString();
}