How to Return an Object with a Collection from a Web API: The Right Approach

Discover how to effectively structure your Web API response to return an object that includes a collection, not just the collection. Learn the steps to achieve this in C# .
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How to Return an Object with a Collection from a Web API: The Right Approach

When building a Web API, one common requirement is to return an object that contains a collection, rather than merely returning the collection itself. For example, within a service method designed to fetch account details and their associated subaccounts, developers often face the issue of not structuring the response as intended. Today, we’ll walk through how to resolve this problem effectively.

The Problem

In the scenario at hand, the intention was to return a main account object at the top level, which includes its subaccounts in a collection. Initially, the API was set up to return a top-level array of subaccounts based on an account ID, and the structure of the JSON response looked like this:

[[See Video to Reveal this Text or Code Snippet]]

This is not the desired output. You want your JSON to be restructured to return the main account along with an array of its subaccounts, like this:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

The root cause of this issue stemmed from the logic within the service method. Instead of returning a Task<IEnumerable<SubAccountViewModel>>, the method should be set to return Task<SubAccountViewModel>. By adjusting this return type and modifying the way data is fetched and structured, we can achieve the desired output.

Implementation Steps

Adjust the Return Type: Change your service method to return Task<SubAccountViewModel> instead of Task<IEnumerable<SubAccountViewModel>>. This allows you to return a single object that contains the collection.

Fetch the Main Account: Obtain the primary account object by querying the database:

[[See Video to Reveal this Text or Code Snippet]]

Fetch Subaccounts: Instead of pulling subaccounts separately, you need to fetch them within the main account structure. Utilize AutoMapper to map the accounts and their associated subaccounts correctly:

[[See Video to Reveal this Text or Code Snippet]]

Return the Final Model: Finally, return the populated subAccountViewModel object, which now contains both the main account details and the associated subaccounts.

Wrap Up

Using this structured approach allows you to return a well-formed JSON object that features both the necessary account information and the related subaccounts. By carefully adjusting your service method’s return type and how you query your database, you can enrich the data structure sent back to your API consumers.

If you face similar issues, applying these principles should help you design API responses that are both effective and meaningful, leading to improved client interactions and data representation.