You can use #Nesting.MultiSelect on a nesting when users need to select multiple rows in its table or grid and use that selection in OCL.

What #Nesting.MultiSelect does

#Nesting.MultiSelect changes a nesting's table or grid from single-row selection to multi-row selection. When this setting is enabled, MDriven maintains a vSelected_ variable for that nesting.

The vSelected_ variable is a strongly typed collection containing the objects that the user has selected. Its postfix is the name of the nesting.

For example, if a ViewModel has a nesting named Order, the selected orders are available through:

vSelected_Order

Use this collection in OCL actions that should operate on all selected objects rather than only the row that currently has focus.

Enable multi-selection

1. In MDriven Designer, locate the blue nesting in the top-level ViewModel that supplies the table or grid.
2. Apply #Nesting.MultiSelect to that nesting.
3. Use the nesting's vSelected_ collection in the OCL for actions that need the selected rows.
4. Run the ViewModel and select more than one row in the grid.

For example, an action can test whether the user has selected any orders before it continues:

vSelected_Order->size > 0

The exact variable name depends on the nesting name. A nesting named Customer has vSelected_Customer; a nesting named Order has vSelected_Order.

vCurrent_ and vSelected_

Do not treat the current row and the selected rows as the same thing:

Variable	Meaning	Example use
vCurrent_	The object the user most recently focused or clicked.	Edit or inspect the current order.
vSelected_	The collection of objects selected when multi-selection is enabled.	Perform an action for every selected order.

MDriven creates and maintains both variables for each ViewModel nesting. Read VCurrent and vSelected before relying on either variable in an action, especially when the action mixes current-row behavior with multi-selection.

First-row selection

WebUI DataGrids automatically select the first row when the list does not use multi-selection. When #Nesting.MultiSelect is enabled, the default is instead not to select the first row automatically.

Set Nesting.AutoSelectFirstRow explicitly to true or false when your ViewModel requires a specific initial-selection behavior. This avoids making an action depend on an assumed current or selected row.

Client considerations

In Turnkey, a row can be included in vSelected_ through the selection control, while vCurrent_ tracks focus. These are maintained as separate concepts. In WPF, focused and selected behavior is naturally differentiated by the UI controls.

Multi-selection is row selection. If you need to select an individual cell or a rectangular group of cells in a native Windows client, use Nesting.CellSelect instead; it is not available in the web client.

See also

• Documentation:Nestings
• Documentation:VCurrent and vSelected
• Documentation:Nesting.CellSelect
• Documentation:Nesting.ClientSortable