Example of rolling up a property on the relationships to the parent

labs_MethodTest.cs

/* 
 * NOTE: This code is a sample to demonstrate how to rollup one level of a relationship.
 *       It is has not been fully tested and should not be used in a production environment as-is.
 */

/* Query for item and relationships happens above */
parentPart = parentPart.apply();

// Get the relationships from your item
Item partBoms = parentPart.getRelationships("Part BOM");

// Add all of the costs of the related parts together
double totalCost = 0;
for (int i = 0; i < partBoms.getItemCount(); i++) 
{
    var partBom = partBoms.getItemByIndex(i);
    var childPart = partBom.getRelatedItem();

    // Quick validation so our parsing logic doesn't fail
    string childCost = childPart.getProperty("cost", "");
    if (!string.IsNullOrEmpty(childCost))
    {
        totalCost += double.Parse(childCost);
    }
}

// Set the total cost on our parent part
parentPart.setProperty("cost", totalCost.ToString());