Blazor Interview Questions & Answers

1. What is Blazor?

   • Answer: Blazor is a web framework by Microsoft that enables developers to build interactive web applications using C# and .NET instead of JavaScript.

2. Explain the difference between Blazor Server and Blazor WebAssembly.

   • Answer: Blazor Server runs on the server and uses a real-time connection to update the UI, while Blazor WebAssembly runs in the browser using WebAssembly for client-side execution.

3. How does Blazor handle rendering and updating of components?

   • Answer: Blazor uses a virtual DOM-like mechanism to efficiently update and render components, ensuring optimal performance.

4. What is Razor in the context of Blazor?

   • Answer: Razor is a syntax used in Blazor for creating dynamic web pages with C# code integrated directly into HTML markup.

5. Explain the concept of Blazor Components.

   • Answer: Components in Blazor are modular, reusable units of code that encapsulate both UI and behavior, facilitating the development of interactive and dynamic web applications.

6. How do you pass parameters to a Blazor component?

   • Answer: Parameters can be passed to a Blazor component using attributes on the component tag in the parent component.

7. What is dependency injection, and how is it used in Blazor?

   • Answer: Dependency injection is a design pattern used to achieve loose coupling between components. In Blazor, services and dependencies can be injected into components using the @inject directive.

8. How does Blazor manage state in a web application?

   • Answer: Blazor provides options for managing state, including component state, cascading parameters, and state containers like IStateContainer.

9. Explain the purpose of the @code block in a Blazor component.

   • Answer: The @code block is where you write the C# code for a Blazor component. It includes event handlers, lifecycle methods, and other component logic.

10. What are Blazor Lifecyle methods?

    • Answer: Blazor lifecycle methods include methods like OnInitialized, OnParametersSet, and OnAfterRender, which allow you to perform actions at different stages of the component's lifecycle.

11. How do you handle user input in a Blazor application?

    • Answer: User input can be handled in Blazor using event handlers such as @onclick, @oninput, and others, similar to traditional HTML event handling.

12. What is the purpose of the @page directive in a Blazor component?

    • Answer: The @page directive is used to specify the route for a Blazor component when building a Single Page Application (SPA).

13. Explain the concept of Razor Pages in Blazor.

    • Answer: Razor Pages in Blazor are standalone .cshtml files that can include both HTML and C# code, allowing for simpler page-based development.

14. What is the role of the NavigationManager in Blazor?

    • Answer: The NavigationManager is used for navigation in Blazor applications, enabling programmatic navigation between pages.

15. How can you integrate JavaScript with Blazor?

    • Answer: JavaScript can be integrated with Blazor using the JSRuntime service, allowing for interop between C# and JavaScript code.

16. Explain the purpose of Blazor Layouts.

    • Answer: Layouts in Blazor define the overall structure of a web page and are used to provide a consistent structure for multiple pages.

17. How does data binding work in Blazor?

    • Answer: Blazor supports both one-way and two-way data binding using the @bind directive for properties and the @oninput event for input elements.

18. What is the significance of the @inherits directive in Blazor?

    • Answer: The @inherits directive is used to specify the base class for a Blazor component, allowing you to inherit from a custom class or one of the built-in Blazor component classes.

19. How do you handle forms and validation in Blazor?

    • Answer: Forms in Blazor can be handled using the EditForm component, and validation can be achieved through data annotations and the ValidationMessage component.

20. What is the role of the HttpClient in Blazor?

    • Answer: The HttpClient is used for making HTTP requests in Blazor applications, enabling communication with APIs and external services.

21. Explain the purpose of @if and @foreach directives in Blazor.

    • Answer: @if is used for conditional rendering, and @foreach is used for iterating over collections and rendering elements accordingly.

22. How can you handle authentication and authorization in Blazor?

    • Answer: Authentication and authorization in Blazor can be implemented using ASP.NET Core Identity, JWT tokens, and policies.

23. What is Blazor WebAssembly lazy loading?

    • Answer: Lazy loading in Blazor WebAssembly allows you to load components and their dependencies on demand, improving application startup performance.

24. Explain the concept of Blazor WebAssembly Hosted model.

    • Answer: In the Hosted model, the server is responsible for hosting the Blazor WebAssembly application, providing benefits like server-side prerendering and better SEO.

25. How can you manage session state in Blazor?

    • Answer: Session state in Blazor can be managed using the Session object or by using services and dependency injection for more complex scenarios.

26. What are the benefits of using Blazor over traditional JavaScript frameworks?

    • Answer: Benefits include code sharing between server and client, using C# throughout the entire stack, and leveraging the .NET ecosystem.

27. Explain the role of the IJSRuntime interface in Blazor.

    • Answer: IJSRuntime is an interface that allows Blazor components to invoke JavaScript functions and interoperate with JavaScript code.

28. How can you handle routing in a Blazor application?

    • Answer: Routing in Blazor can be handled using the @page directive, the NavigationManager service, and routing templates.

29. What is the purpose of the CascadingValue component in Blazor?

    • Answer: CascadingValue is used to pass a value down the component tree, making it available to descendant components without the need for explicit parameter passing.

30. Explain the significance of the AuthorizeView component in Blazor.

    • Answer: AuthorizeView is used to conditionally render content based on the user's authentication status, allowing you to show different UI elements for authenticated and unauthenticated users.

31. How do you handle errors in a Blazor application?

    • Answer: Errors in Blazor can be handled using try-catch blocks, global error handling in the App.razor file, or by subscribing to the `OnUnhandleException

` event.

32. What is the role of the @key directive in Blazor?

    • Answer: @key is used to provide a unique identifier for items in a collection, enabling efficient updates and rendering in loops.

33. How can you integrate Blazor with SignalR for real-time communication?

    • Answer: Blazor can be integrated with SignalR for real-time communication by using the HubConnection and the @code block to handle events.

34. Explain the purpose of the AuthenticationStateProvider in Blazor.

    • Answer: AuthenticationStateProvider is used to obtain the current authentication state, providing information about the user's identity and roles.

35. What is the role of the @ref directive in Blazor?

    • Answer: @ref is used to create a reference to a component or an HTML element, allowing you to interact with it programmatically.

36. How can you use JavaScript libraries in a Blazor application?

    • Answer: JavaScript libraries can be used in a Blazor application by integrating them using the IJSRuntime service and calling JavaScript functions.

37. What is the purpose of the StateHasChanged method in Blazor?

    • Answer: StateHasChanged is a method that forces a re-render of a Blazor component, useful when the state changes outside of normal event handling.

38. How do you handle Blazor component events in parent components?

    • Answer: Blazor components can communicate with parent components using events. The parent component can subscribe to these events and respond accordingly.

39. Explain the role of the RenderMode in Blazor Server.

    • Answer: RenderMode is used to control how a component renders on the server, specifying whether it should render as a block or as an inline element.

40. How can you secure a Blazor WebAssembly application?

    • Answer: Security in Blazor WebAssembly can be implemented using authentication, authorization policies, HTTPS, and securing API endpoints.

41. What is the purpose of the CodeBehind files in Blazor?

    • Answer: CodeBehind files in Blazor are used to separate the code logic from the markup, improving code organization and maintainability.

42. Explain the concept of Dependency Injection in Blazor.

    • Answer: Dependency Injection in Blazor is a mechanism for providing components with the services and dependencies they need, promoting modularity and testability.

43. How can you handle file uploads in Blazor?

    • Answer: File uploads in Blazor can be handled using the InputFile component and the HttpClient to send the file to the server.

44. What is the role of the ITestOutputHelper interface in Blazor testing?

    • Answer: ITestOutputHelper is an interface used for capturing test output in unit tests, providing a way to log messages during testing.

45. How can you handle global error handling in a Blazor application?

    • Answer: Global error handling in Blazor can be implemented by subscribing to the OnUnhandleException event in the Program.cs file.

46. Explain the concept of Scoped Services in Blazor Dependency Injection.

    • Answer: Scoped Services in Blazor Dependency Injection are services that are created once per request or once per scope, providing a single instance for the duration of a user's interaction with the application.

47. What is the purpose of the CaptureUnmatchedValues attribute in Blazor?

    • Answer: CaptureUnmatchedValues is an attribute used to capture HTML attributes that are not explicitly bound to properties in a Blazor component.

48. How can you improve the performance of a Blazor application?

    • Answer: Performance in Blazor can be improved by optimizing the use of services, minimizing unnecessary renders, and implementing lazy loading where applicable.

49. Explain the purpose of the Microsoft.AspNetCore.Components.Authorization namespace in Blazor.

    • Answer: The Microsoft.AspNetCore.Components.Authorization namespace provides classes and interfaces for handling authentication and authorization in Blazor applications.

50. What is the role of the @inherits directive in Blazor?

    • Answer: The @inherits directive is used to specify the base class for a Blazor component, allowing you to inherit from a custom class or one of the built-in Blazor component classes.