The filter string should be valid, standard SQL to be added to the 'WHERE' clause sent to the Data Source. This filter string can include Exago system parameters (e.g. @userId@) or custom SQL including subqueries (e.g. IN (SELECT EmployeeID FROM Employees WHERE EmployeeID <4)). The Filter String must contain the actual name of objects in the Data Source (e.g. tables, views, columns, etc...)  (the Entity.DbName Property) rather than their Exago aliases.

public System.string FilterString {get; set;}