To display, in your web screens, a list with the values of a specific attribute plus some special (generic) values like, for example, All and None, you have to use the Combo Box widget as described below.

Typically this is used when there are other possibilities beyond the contents of a list. The list is ordered by that specific attribute but at the top of the list there are always the special values.

You can add special values in any of the following situations:

How to implement this behavior:

Simply use the following properties of the Combo Box widget:

  • Source Entity/Structure: Name of the entity whose attribute you want to display.

  • Source Attribute: Name of the attribute whose contents you want to display. You have access to all the available attributes of the selected entity.

  • Variable: Variable that will hold the identifier of the row that corresponds to the end-user's selection, after it is submitted, if this selection refers to a value of the Source Entity / Structure.

During the preparation of the screen, this property can be used to set a default value.

  • Special Variable: Variable that will hold the Value of the end-user's selection, after it is submitted, if this selection refers to a value of the Special List.

The variable must be of type Text, Phone Number, Email, Boolean or Integer, otherwise an error message is presented and the eSpace is not valid. You can also set a default value for this property in, for example, the preparation of the screen.

  • Source Record List: Only if you want to filter the rows to be selected.

  • Special List Properties Group: Add all the options values and the options texts that must be presented.

The Name and Width properties must also be filled-in. How?

Handling the end-user's selection

In this situation, there are two different, and exclusive, ways to handle the end-user choice: by the Variable property or by the Special Variable property.

These mechanisms are completely transparent to you and it is the responsibility of Platform Server to correctly managed this situation.


Suppose you want to display the attribute Name of all the rows of the entity Product and, also, give the end-user the possibility of selecting none or all products. You just have to use the Combo Box widget as following:

      • Source Entity: Product

      • Source Attribute: Name

      • Variable: ProductId

      • Special List Group:



Value 1


Option 1

None of the Products

Value 2


Option 2

All Products


The list has all the names that exist on the entity Product, ordered by Name.

If the end-user chooses an option from the list, the variable ProductId contains the id of the product that corresponds to that choice.

If, on the other hand, the end-user selects “None of the Products” or “All Products”, the Special Variable contains 0 or -1, respectively.

See Also

Combo Box Widget Properties | About Combo Box Widget