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Provide a descriptive title for the template and then paste (or type) the common expression into the Template text box. Click "Add". Then click "Close".
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To insert the common expression into the business logic for an element, choose "Enter Mapping Business Logic" from the "Mapping Method" drop-down menu, then click inside the Business Logic business logic text box. Click the double arrow << to expand the "Templates" menu, then select the desired template from the list.
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