Steven,

You should have two overloads of GetOrderDetail in your business object...one that accepts a parameter of type int(as specified in step 6):

public DataSet GetOrderDetail(int orderID)
{
	return this.GetDataSet("SELECT * FROM [Order Details] WHERE OrderID = " + 
				orderID);
}

And a second overload that accepts a parameter of type object (as specified in step 7):

public DataSet GetOrderDetail(object orderID)
{
	if (orderID != null)
	{
		return this.GetOrderDetail((int)orderID);
	}
	else
	{
		return this.GetEmptyDataSet();
	}
}

If you didn't add the first overload as specified in step 6, this would create a recursive call situation.

Regards,