How to – Use Custom API to create custom messages in Dynamics 365

Custom API (preview) allows us to define our custom messages that can be called from web services, similar to Custom Actions. Usually, we would be creating custom workflow actions just to create a new message, to which we can hook our plugin, without defining any logic in the workflow. For this scenario or pattern now we can use Custom API instead.

There are different ways of creating a custom API.

Through the Maker Portal.
Using Web API or Organization Service.
Editing the solution files.

The 3 key entities involved here are

CustomAPI
CustomAPIRequestParameter
CustomAPIResponseProperty

Let us try creating a CustomAPI through the maker portal.

Create a new solution, and click on New and select Custom API

Let us start with a very basic custom action.

Unique Name	This will be the name of the message. Should have the prefix same as solution’s publisher.
Name	The name of the Custom API will show up inside the solution
Display Name	Localized display name of the Custom API
Description	Localized description of the Custom API
Binding Type	Value: 0 Label: Global Value: 1 Label: Entity Value: 2 Label: EntityCollection
Bound Entity Logical Name	Logical name of the entity in case of binding type – Entity and EntityCollection.
Is Function	Value: 0 Label: No Value: 1 Label: Yes
Allowed Custom Processing Step Type	Value: 0 Label: None Meaning: No custom processing steps allowed. Value: 1 Label: Async Only Meaning: Only asynchronous custom processing steps allowed Value: 2 Label: Sync and Async Meaning: No restriction. 3rd party plug-ins can add synchronous logic to change the behavior of the message
Execute Privilege Name	Name of the Privilege that is required for the execution of the Custom API.
Plugin Type	Reference of the plugin registered for the Custom API

So right now we have a very basic custom API registered of Global type, which doesn’t allow any steps to be registered and doesn’t need any privileges to execute

Let us write a sample plugin and associate with this new message.

Let us register the assembly

Now let us go back to our Custom API record and associate the Plugin registered.

Let us trigger the plugin by calling the Custom API through the Postman.

Let us check the plugin trace log inside Dynamics 365 App.

Get all details here

https://docs.microsoft.com/en-us/powerapps/developer/data-platform/custom-actions

Hope it helps..

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