Solving the ApplicationUser Injection Issue in ASP.NET Core 3.1 Views

Описание: Learn how to resolve the `ApplicationUser` injection error in your ASP.NET Core 3.1 project. This guide provides a step-by-step approach to troubleshooting and fixing your view issues effectively.
---
This video is based on the question https://stackoverflow.com/q/65529801/ asked by the user 'Ahsan Shuvo' ( https://stackoverflow.com/u/4282721/ ) and on the answer https://stackoverflow.com/a/65558206/ provided by the user 'Fei Han' ( https://stackoverflow.com/u/6751634/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Failed to Inject extended IdentityUser in view in AspNetCore 3.1

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Troubleshooting ApplicationUser Injection Issues in ASP.NET Core 3.1 Views

ASP.NET Core is a powerful framework that allows developers to build web applications quickly and efficiently. However, issues can sometimes arise during development, especially when it comes to user authentication and identity management. One common problem developers encounter is the inability to inject a custom ApplicationUser that extends IdentityUser into their views. In this guide, we will discuss how to resolve the error message: "the type of namespace ApplicationUser cannot be found (are you missing a using directive or an assembly reference)".

Understanding the Problem

Before we dive into the solution, let’s clarify the context:

You have created a custom user class, ApplicationUser, which extends the built-in IdentityUser.

When trying to inject ApplicationUser into a partial view (_signinPartial.cshtml) for display logic (like showing login/logout options), you encounter a compilation error.

Your _ViewImports.cshtml correctly imports the necessary namespaces, but the error persists.

Step-by-Step Solution

Here are the steps you should follow to troubleshoot and resolve this issue:

1. Check Namespace Definition

Ensure that your ApplicationUser class is defined within the correct namespace. It should look similar to the following:

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

2. Verify _ViewImports.cshtml

The _ViewImports.cshtml file plays a crucial role in managing namespaces across your views. Ensure that you have imported the correct namespace for ApplicationUser. Your _ViewImports.cshtml should include:

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

3. Understand File Scoping

Be aware that _ViewImports.cshtml files can exist in different folders. If you have multiple _ViewImports.cshtml files, make sure the correct one is being used for your view. The imports will only apply to views within the same folder and subfolders.

4. Use Fully Qualified Names

As a workaround, you can use the fully qualified name of your ApplicationUser when injecting it in your partial view to avoid ambiguity. Change your injection code as follows:

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

5. Additional Imports

Double-check that you've imported the necessary namespaces in your _ViewImports.cshtml, including both Microsoft.AspNetCore.Identity and your custom model namespace:

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

Conclusion

By carefully verifying the definition of your ApplicationUser class, ensuring that the correct namespaces are imported, and understanding the scope of your _ViewImports.cshtml, you can effectively resolve the injection issue. Remember, if you find yourself stuck, don’t hesitate to employ the fully qualified class name as an alternative solution.

If you have any further questions or need more help with ASP.NET Core identity or any other topic, feel free to reach out in the comments!