The following example shows a .NET Framework function being called within a query (WHERE clause). It filters the orders in the Northwind Orders table so that only orders withing the last 6 years are displayed.
For the custom function, use the DateTime.Now() Visual Basic .NET function which returns the current time. To display orders within the past 6 years, call the AddYears method with negative 6 as its parameter. Convert this to a string format required by the SELECT statement using the ToString() directive.
DateTime.Now.AddYears(-6).ToString()
On the left-hand side of the clause, select the Order Date field in the Orders table. The WHERE clause is:
Orders.OrderDate < DateTime.Now.AddYears(-6).ToString()
Calling Custom Code Functions in WHERE Clauses
Example: Calling a .NET Framework Function
Example: Calling a Custom Function in a Customizable Class