Sum of LineItems

[Chicagoan2016]

We are migrating a non-csla application to Csla. We have line items (collection) contained in an order object.
How should we implement total amount of line items contained in a particular order object? A business rule that gets called when we save the order object and update a property 'Totalamount'?

Regards

[TheCakeMonster]

Do you need a property on the parent? I wonder if instead you can dynamically sum the totals from the child collection.

[Chicagoan2016]

You mean without a rule?

[TheCakeMonster]

@Chicagoan2016 Yes, without a rule. There's nothing wrong with creating a rule, but it doesn't really sound like you need it. Just iterate over the items in the child collection in your Create and Update methods. Iteration over a local collection is so fast it's virtually unmeasurable. Having a rule will cause the rule to run every time any child's price changes, or any child is added or removed. That's a lot of times in a normal UI.

YAGNI.

[kcabral817]

If you have to have the total calculated after a read from the persistence store, I would lean towards a business rule. Regards Kevin

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________________________________ From: TheCakeMonster ***@***.***> Sent: Tuesday, November 1, 2022 3:38:44 PM To: MarimerLLC/csla ***@***.***> Cc: Subscribed ***@***.***> Subject: Re: [MarimerLLC/csla] Sum of LineItems (Discussion #3182) Do you need a property on the parent? I wonder if instead you can dynamically sum the totals from the child collection. — Reply to this email directly, view it on GitHub<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FMarimerLLC%2Fcsla%2Fdiscussions%2F3182%23discussioncomment-4031503&data=05%7C01%7C%7Cf011409f35264000872c08dabc59d55d%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638029391253742592%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Ox2Zv%2B7jLcbjEfi67F9w8mzeVrPaFA7zAPPDNekpT94%3D&reserved=0>, or unsubscribe<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnotifications%2Funsubscribe-auth%2FAGJTVDQRX5NUTZ2VLK563K3WGGLXHANCNFSM6AAAAAARUOV5CQ&data=05%7C01%7C%7Cf011409f35264000872c08dabc59d55d%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638029391253742592%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Esg2OtGEMAzyE3%2BEkadSnQaReApFOj3RTd4pGxmg1lQ%3D&reserved=0>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Chicagoan2016]

No, it will be calculated only on 'Save'.

[kcabral817]

You have some options then. You can perform the calculation in the save method, business rule, or in the view model. However, I would still lean towards a business rule and then you can leverage that rule if the business rule changes and folks want it calculated real-time or at some other point in the process flow. Here are two methods that I use to intercept a property change value and perform some work. These are in my business class and you can add an if statement to check for the property that has the values and then sum them and do it real time. protected override void PropertyHasChanged(IPropertyInfo property) { base.PropertyHasChanged(property); BusinessRules.CheckRules(); BusinessRules.CheckObjectRules(); } protected override void OnChildChanged(ChildChangedEventArgs e) { base.OnChildChanged(e); BusinessRules.CheckRules(); } I invoke the business rule stream but you can sum the values and they will be displayed when changed. Regards, Kevin From: ***@***.***> Sent: Wednesday, November 2, 2022 9:31 AM To: ***@***.***> Cc: Kevin ***@***.***>; ***@***.***> Subject: Re: [MarimerLLC/csla] Sum of LineItems (Discussion #3182) You mean without a rule? — Reply to this email directly, view it on GitHub<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FMarimerLLC%2Fcsla%2Fdiscussions%2F3182%23discussioncomment-4039805&data=05%7C01%7C%7C743b89403f354dc5b66708dabcefa909%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638030034756602568%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=%2BJqQ8NC33L1OQwBZpaJUcAgHu4SzNwfQ7BAlDWrrfD4%3D&reserved=0>, or unsubscribe<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnotifications%2Funsubscribe-auth%2FAGJTVDUEINLS4K5LWXRTD3DWGKJNFANCNFSM6AAAAAARUOV5CQ&data=05%7C01%7C%7C743b89403f354dc5b66708dabcefa909%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638030034756602568%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=fY8y0F7YA3eb4gHwElJvV8uI7aBRZnNgPjFigsoJbOk%3D&reserved=0>. You are receiving this because you commented.Message ID: ***@***.***>

[Chicagoan2016]

@kcabral817
Kevin,
We have another use case which involves children and grand children. I am going to follow your approach but I was wondering what's the use of

    protected override void PropertyHasChanged(IPropertyInfo property)
     {
         base.PropertyHasChanged(property);
         BusinessRules.CheckRules();
         BusinessRules.CheckObjectRules();
     }

?
Kind Regards

[kcabral817]

There are times when a specific property changes that I want to invoke the rules. This was mainly for WPF and my not be applicable to Blazor

[rockfordlhotka]

@Chicagoan2016 also keep in mind that you can use the ChildChanged event to detect changes in children within your object graph. That exists specifically to aid in implementing scenarios where a parent needs to run rules based on the fact that a child or grandchild or whatever has been changed.

[Chicagoan2016]

@rockfordlhotka I think we have to use 'Target' property in a business rule like this or could we implement it without 'Target'?
Regards