ASP.NET MVC is a popular framework for building web applications using the Model-View-Controller architecture. While it offers a lot of advantages, developers can easily fall into common traps that can lead to inefficient, hard-to-maintain code. Here, we will explore ten common mistakes made in ASP.NET MVC development and provide tips on how to avoid them.

1. Ignoring Convention over Configuration

ASP.NET MVC follows the principle of “Convention over Configuration,” which helps in reducing the amount of code needed to configure the application. Many developers, especially those new to the framework, may ignore this principle.

• Mistake: Over-configuring routes, view names, and action results.
• Solution: Familiarize yourself with the conventions used in ASP.NET MVC. For instance, if you name your controller as HomeController, the framework expects your views to be in a folder named Home.

2. Not Using Action Filters

Action filters are an essential part of the ASP.NET MVC pipeline, allowing developers to run code before and after an action method executes.

• Mistake: Repeating code for cross-cutting concerns.
• Solution: Use action filters to handle tasks like logging, authorization, or caching. Create custom filters when necessary to encapsulate this functionality effectively.

3. Poorly Structured Models

Models are the backbone of any MVC application, representing the data and business logic. Poor structuring of models can lead to performance issues and code that is hard to maintain.

• Mistake: Keeping all logic within the model without breaking it into smaller services.
• Solution: Separate concerns by using Data Transfer Objects (DTOs) and service classes. This promotes cleaner code and easier testing.

4. Hardcoding Strings

Hardcoding strings can lead to maintenance headaches if changes need to be made in multiple places.

• Mistake: Using raw string literals throughout the application.
• Solution: Utilize resource files or constants to manage strings. This not only centralizes your string literals but also aids in localization efforts later.

5. Neglecting Model Validation

Validation plays a critical role in ensuring data integrity. Failing to implement validation can lead to incorrect data being stored in the database.

• Mistake: Relying solely on client-side validation.
• Solution: Implement both client-side and server-side validations using Data Annotations or custom validation attributes. Always validate on both ends to ensure that invalid data is not processed.

6. Excessive Use of ViewBag/ViewData

The ViewBag and ViewData are dynamic objects used to pass data from controllers to views, but excessive use can clutter your code.

• Mistake: Relying heavily on ViewBag and ViewData for passing data.
• Solution: Use strongly typed models instead. This practice provides better compile-time checking and IntelliSense support in your views, making your code cleaner and more maintainable.

7. Failing to Use Dependency Injection