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Discover how to easily obtain the `UserId` of the current user in your Blazor WebAssembly application with ASP.NET Core Identity.
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This video is based on the question https://stackoverflow.com/q/63104080/ asked by the user 'Gary Jurgens' ( https://stackoverflow.com/u/11562067/ ) and on the answer https://stackoverflow.com/a/63108016/ provided by the user 'Brian Parker' ( https://stackoverflow.com/u/1492496/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Retrieve UserId of the Current User in Blazor WebAssembly Using ASP.NET Core Identity

When developing applications with Blazor WebAssembly, you may encounter a common need: obtaining the UserId of the currently authenticated user. This requirement becomes especially important in scenarios where you need to associate user data with a foreign key in your models or tables. In this guide, we will explore the steps to achieve this using ASP.NET Core Identity.

The Challenge

In ASP.NET Core Identity, various methods are available to retrieve user information. However, developers often find themselves facing a limitation: only the username is typically returned. This can pose a problem since usernames are subject to change, but the UserId remains constant. Therefore, knowing how to retrieve the UserId directly is crucial for ensuring your application functions reliably.

A Simple Solution

To obtain the UserId of the current user in a Blazor WebAssembly application, we can utilize the built-in capabilities of the AuthenticationStateProvider. Below, we'll break down the code that provides this functionality.

Code Breakdown

Here’s a simplified version of the component that retrieves the current user's UserId:

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

Explanation of the Code

Injecting AuthenticationStateProvider: This is crucial as it provides the authentication state of the user.

Fetching User Claims: Once we have the user's authentication state, we check if the user is authenticated and fetch their claims.

Obtaining the UserId: The sub claim, which stands for "subject," is typically used to store a unique identifier for the user. This is accessed using user.FindFirst(c => c.Type == "sub")?.Value.

Result

After implementing the above code, you will be able to retrieve the UserId of the current user whenever needed. You can then utilize this ID to establish connections between users and their associated records in your database.

Conclusion

In summary, obtaining the UserId of the current user in a Blazor WebAssembly application using ASP.NET Core Identity can be achieved with relatively straightforward logic. By leveraging the AuthenticationStateProvider and understanding how to access user claims, you can ensure that your application properly manages user identity in a way that remains consistent—even if usernames change over time.

By following the steps outlined in this post, you can enhance your application’s functionality and provide a better experience for your users.

If you have any questions or need further clarification, feel free to ask in the comments!