Dynamics CRM–Business Rules or Workflows?

When should you use a business rule (BR) and when should you use workflows?

First thing we should understand are that business rules are just another type of a process (just like Workflows and Business Process Flows). You can validate this by performing an advanced find and setting the category to Business Rule. Other options for category are:

Now when you create a business rule, there are 3 options (2 really), one that applies it to forms (all or specific) and the other that applies it to the entity. When you choose entity and create your BR, and activate it, you will find 2 entries in processes with the same name. One of these handles the javascript part (that gets run client side). The other is a synchronous workflow that runs on create and on update of the fields that are in conditionals of the business rule. You can look at the JavaScript that will run by looking at the ClientData field on Process. Also, the XAML field contains workflow.

Why is this important to know? Here is why:

1. If you have a business rule that needs to be run client side, then Business Rules are your best option. This is especially true if you want to show error messages or perform data validation.

2. But if you are going to have an entity level business rule and it doesn't really contain validation or error messages, then you have a choice: If you use a Workflow, you can decide to run it in the background (asynchronously).

Some other things to consider:

Business Rules have a nicer UI. But, every business rule that fires at the entity level creates a new synchronous workflow that fires on create and on update of a single field. If you use a workflow, you have more choices: you can create a single workflow that runs on Create, that does all the things that need to be done on create, this in my opinion is more efficient, then having multiple workflows that are all firing one after the other.

Also, look at the limitations of BR as defined in microsoft docs: https://docs.microsoft.com/en-us/previous-versions/dynamicscrm-2016/admins-customizers-dynamics-365/mt826761(v=crm.8)#limitations

Inner workings of Business Rule javascript:

Finally, if you are curious about the inner workings of business rules, see the code at: https://github.com/rajrao/CRM-Tools/tree/master/JavaScript/BusinessRules

But basically here are the main things to know:

The javascript for the business rule is injected into the formscript for the form.
The function itself is setup to run on change of the fields that are in the conditionals.
The function is run once at form startup.