Is there a way to do a transactional query/lookup for different types of documents with a common partitionKey stored in the same container

I have a CosmosDB container in Azure and it contains documents of three types (typeA, typeB, and typeC). There is only one typeA for every key, and multiple documents of typeB and typeC for each key (ex. typeA is a user profile with an id (which acts as the paritionKey), and typeB is an order made by that user, and typeC is a review written by that user -- typeB and typeC both use the user id as their partitionKey). How do I write a transactional operation to read all documents for a given user id? I'm hoping to do a point lookup of typeA, and a ReadManyAsync for typeB and typeC in a transactional manner.

Example data:

object of typeA

{

userId: 01234
lastPurchase: 01-02-2023

}

object of typeB

{

userId: 01234
purchaseId: 56789
purchaseQuantity: 1

}

object of typeC

{

userId: 01234
lastReviewWritten: 01-02-2023
reviewId: 101112

}

This is what I've tried:

container.Database.BeginTransactionAsync()

issue - Database does not have the BeginTransactionAsync() property

container.CreateTransactionalBatch(new PartitionKey("/beneficiary"))
.ReadItem(beneficiary).ExecuteAsync()

issue - as far as i can tell this is only for one type of document at a time. If the type is not an issue for the read, do I just deserialize into typeA, typeB, and typeC in this function (by adding a 'type' property to each data type)?

If you are trying to read multiple documents at the same time, the easiest way is to use a query. In your case, SELECT * FROM c WHERE c.userId = '01234'.

Because you are dealing with multiple entities, you will need to define the query and result set as a dynamic datatype, then inspect whatever property you are using to determine the entity, and deserialize into its appropriate object.

You see an example of this in this function here, QueryCustomerAndSalesOrdersByCustomerId() from the Cosmic Works Sample on GitHub.

In fact this example is nearly identical to your scenario in that the data is queried from a container that contains one customer profile document and all of that customer's sales orders. The container is partitioned by customerId.