.NET Core 3.1 WebAPI中AWS Cognito用户组信息获取与排序功能问询

Hey there! Let's break down your two AWS Cognito SDK questions for your .NET Core 3.1 WebAPI project:

Unfortunately, AWS Cognito doesn’t offer a single out-of-the-box API that returns both full user profiles and their associated groups. The ListUsers endpoint only returns core user attributes, and ListUsersInGroup requires targeting individual groups—something that gets costly if you have lots of users or groups.

Here are some practical workarounds I’ve used in similar projects:

• Sync group info to user custom attributes: Use a Cognito Lambda trigger (like PostAuthentication or PostConfirmation) to update a custom user attribute (e.g., custom:userGroups) whenever a user joins or leaves a group. Then you can retrieve this attribute directly via ListUsers. Just note you’ll need to handle edge cases like group deletions to keep the attribute in sync.
• Batch group-to-user mapping: First call ListGroups to get all your pool’s groups, then batch call ListUsersInGroup for each group. Once you have all users per group, you can map them to their respective groups in your .NET code. This is more efficient than querying groups per user, especially if you have fewer groups than users.
• Offload to a secondary store: Sync user and group data to a DynamoDB table (using Lambda triggers) whenever changes happen. Then you can query DynamoDB directly for joined user-group data with a single request, avoiding repeated Cognito API calls entirely.

You’re right—Cognito’s ListUsers API doesn’t support built-in sorting by fields like name or email. It only offers filtering capabilities. To handle sorting, you have two main options:

• Client-side sorting: Fetch the user list via ListUsers (handling pagination if needed) and then sort the results in your .NET code using LINQ. For example:

  var users = await cognitoClient.ListUsersAsync(new ListUsersRequest { UserPoolId = "your-pool-id" });
  var sortedUsers = users.Users.OrderBy(u => u.Attributes.First(a => a.Name == "email").Value).ToList();
  

  Just keep in mind this only sorts the current page of results. If you need global sorting across all users, you’ll have to fetch all pages first (which isn’t ideal for large user pools).
• Use a secondary sorted store: If you’re dealing with a large number of users, sync user data to a DynamoDB table with a sort key on the field you want to sort by (e.g., email or name). Then you can query DynamoDB with a sorted scan/query to get ordered results efficiently.

内容的提问来源于stack exchange，提问作者Ask