Query() and While Select in X++

We can use Query() class or while select statement to create a query on the table.

using while select statement

while select InventTable

ItemId == "123ABC";

using Query class

Query = new query();

query.addDataSource(tableNum(InventTable)).addRange(fieldNum(InventTable, itemId)).value("123ABC");

List Page Interaction classe Ax 2012

class SPLPayLeaveEncashListPageInteraction extends ListPageInteraction
{
    SPLPayLeaveEncash   SPLPayLeaveEncash;
}

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public void selectionChanged()
    {

        SPLPayLeaveEncash = this.listPage().activeRecord(queryDataSourceStr(SPLPayLeaveEncashListPage, SPLPayLeaveEncash));

        super();

            if(SPLPayLeaveEncash.Approved == NoYes::Yes || SPLPayLeaveEncash.ProcessWithSalary == NoYes::Yes  )
        {
            this.listPage().actionPaneControlEnabled(formControlStr(SPLPayLeaveEncashListPage, DeleteCommandButton), false);
        }
        else
        {
            this.listPage().actionPaneControlEnabled(formControlStr(SPLPayLeaveEncashListPage, DeleteCommandButton), true);
        }
    }