Scenario

I have a smartobject associate with web service (asmx) and return List<Customer>, with 2 arameters (FirstName,LastName) I am able to execute the List method under smartobject tester and it could pass NULL to my web service and retrieve all customer information. 

Result in smartform

When I want to create a search form under smartform, I could not pass the null value to the listview as it prompt me to enter the required property (FirstName, LastName)