How to Efficiently Extract JWT Token Claims in a Blazor Application

Learn how to retrieve specific JWT token claims like the customer's first name from a Blazor page efficiently using an extension method. --- This video is based on the question https://stackoverflow.com/q/74649623/ asked by the user 'GluhaiaMuha' ( https://stackoverflow.com/u/14072710/ ) and on the answer https://stackoverflow.com/a/74650400/ 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. 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: How to get Jwt token Claim from a blazor page? Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- How to Get JWT Token Claims from a Blazor Page In the world of web applications, JSON Web Tokens (JWT) are commonly used for authentication and providing authorization. They serve as a compact and secure way to transmit information between parties. When developing a Blazor application that utilizes JWT authentication, a common challenge arises: how to efficiently extract and display information embedded within these tokens. This guide explores a practical solution to retrieve JWT claims, particularly focused on accessing user details such as a customer's first name, last name, and credits from a Blazor page. The Problem As developers, we often encounter scenarios where we need to access user-specific information stored in a JWT. For example, you might want to create a profile page that displays customer details such as: First Name Last Name Credits In a Blazor razor page, you may have noticed that using the following code: [[See Video to Reveal this Text or Code Snippet]] yields results in the format FirstName:Bob, which is not ideal when you want to simply display the name Bob. Additionally, someone might prefer a more elegant and efficient method for retrieving these claims that mirrors the convenience of using -context.User.Identity.Name. A Solution: Extension Method to Get Claims To streamline the retrieval of specific JWT claims, you can create a custom extension method. This allows you to easily access any claim from the ClaimsPrincipal without cluttering your razor files with repetitive code. Here's how to implement this solution step by step: Step 1: Create the Extension Method First, create a static class for your extension method. In this class, define a method that retrieves the value of a specified claim type. The following code demonstrates how to implement this: [[See Video to Reveal this Text or Code Snippet]] In this code snippet: We create an extension method called GetClaimValue for ClaimsPrincipal. It checks for a claim of the specified type and returns its value. If the claim isn’t found, it gracefully returns an empty string. Step 2: Use the Extension Method in Your Blazor Page Now that you have defined the extension method, you can conveniently use it in your Blazor pages. Here's how you can retrieve the first name claim: [[See Video to Reveal this Text or Code Snippet]] Simply replace "FirstName" with the appropriate claim type you wish to retrieve. This method call returns the value of the claim directly, making your code cleaner and more maintainable. Conclusion By using a custom extension method, you can efficiently extract JWT claims in a clean and readable manner in your Blazor applications. This approach not only enhances the clarity of your code but also reduces redundancy. You can now easily display user details on your profile page, enriching the user experience of your application. Feel free to adapt and expand upon the basic example provided here to fit your specific use cases, and happy coding with Blazor!