>Hi,
>
>I may have asked this before, my apologies if I have, but I can't work out how to do this.
>
>I have a Receipt BO and a ReceiptDetails BO which is a child of the Receipt BO. For data entry validation, the user has to enter a total amount received at the Receipt BO level and then the sum of the amounts entered at the Receipt Detail BO level must equal the Receipt BO's total amount received.
>
>How should I approach writing such a Business Rule?
>
>I guess it should be at the Receipt BO level, but how would I refer to the child BO to sum all the amounts?

I spent some time with Josh this morning looking at why the gridview is not showing the error icon (see my other thread on that) and asked him how he would approach this. Here's what he came up with:

In my ReceiptDetailRules.Partial.cs I created a method:

        public string CheckReceiptTotal(Decimal? ReceiptAmount, DataSet dsReceiptDetails)
        {
            string message = null;
            Decimal sumAmountReceived = 0;
            foreach (DataRow Row in dsReceiptDetails.Tables["ReceiptDetails"].Rows)
            {
                sumAmountReceived += (Decimal)Row["AmountReceived"];
            }
            if (sumAmountReceived != ReceiptAmount)
            {
                message = "The sum of the Split Amount values does not match Total Amount Received";
                AddErrorProviderBrokenRule("AmountReceived", message);
            }
            return message;
        }

In ReceiptDetail.Partial.cs I added a new property:

public Decimal ParentReceivedTotal = 0;

and created this hook override which sets the property when saving to the value entered on the Parent BO:

Update: changed HookParentSaving to HookParentPreSaving as this fires before the child gets saved whereas the HookParentSaving fires after the child has been saved

        protected override void HookParentPreSaving(mmBusinessObject bizObj, mmBusinessStateChangeEventArgs e)
        {
            Receipt oParent = bizObj as Receipt;

            ParentReceivedTotal = oParent.Entity.ReceiptAmount;
            base.HookParentSaving(bizObj, e);
        }

Then in ReceiptDetailRules.cs I added this code to the CheckRulesHook just prior to the return statement:

            if (this.ErrorProviderBrokenRuleCount == 0 && entityList.Count > 0)
            {
                ReceiptDetail oReceiptDetail = (ReceiptDetail)this.HostObject;
                ReceiptDetailEntity oReceiptDetailEntity = entityList[0] as ReceiptDetailEntity;
                this.CheckReceiptTotal(oReceiptDetail.ParentReceivedTotal, oReceiptDetailEntity.GetDataRow().Table.DataSet);
            }

I hope this helps someone else.