Скачать или смотреть Resolving Aggregate Exception in Asp.Net Core 5.0: A Guide for File Uploaders

Learn how to resolve `Aggregate Exception` in your Asp.Net Core 5.0 project and effectively implement file upload functionality with our detailed guide.
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Resolving Aggregate Exception in Asp.Net Core 5.0: A Guide for File Uploaders

When working on a project in Asp.Net Core 5.0, you might encounter an Aggregate Exception related to dependency injection. This issue often arises when certain services cannot be constructed due to unresolved dependencies. If you're dealing with file uploads through a layered architecture, as seen in Mvc projects, you may run into this problem, especially with services like IFileUploader and related models. In this guide, we will explore the problem and provide a clear solution to overcome this hurdle.

Understanding the Problem

In your case, you have an IFileUploader interface with a corresponding FileUploader class that requires a FileModel as part of its construction. The error message indicates that the FileModel class is not registered with the IoC (Inversion of Control) container in your Asp.Net Core application, which leads to the inability to activate the FileUploader class.

Error Message Breakdown

The error message you received reads as follows:

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

This means that when Asp.Net Core attempts to create an instance of FileUploader, it can't find an instance of FileModel that it needs. This commonly happens if you forget to register FileModel within your Startup.cs configuration.

Solution: Registering FileModel in the IoC Container

To resolve this issue, you need to ensure that the FileModel class is registered in the dependency injection container. Here’s how you can do that:

Step 1: Update Your Startup.cs

Open your Startup.cs file and locate the ConfigureServices method. You need to add a line that registers your FileModel class. This can be done as follows:

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

Step 2: Choose the Appropriate Lifetime

In the example above, we used AddSingleton to register FileModel. This specifies that a single instance of FileModel will be created and reused throughout the application's lifetime. Depending on your requirements, you might opt for a different lifetime:

AddScoped: A new instance is created for each request. This is useful if FileModel holds state that is specific to a user's request.

AddTransient: A new instance is created each time it is requested. This is useful for lightweight or stateless services.

Step 3: Test Your Implementation

After making these changes, rebuild your project and run it again. Your FileUploader class should now instantiate correctly, and the file uploading functionality should work as intended.

Conclusion

In this post, we tackled the common Aggregate Exception issue in Asp.Net Core 5.0 projects, particularly when working with file upload functionalities and multi-layer architectures. By understanding dependency injection and properly registering your services within the IoC container, you can avoid these pitfalls and create a smoothly functioning application. Don’t hesitate to revisit this guide if you face similar challenges in the future.

Thanks for reading! We hope this has clarified how to resolve your issues with FileUploader in Asp.Net Core 5.0.