How to Implement Validation Only Once for Properties and Commands?

Are you tired of writing repetitive validation code for your properties and commands? Do you wish there was a way to simplify this process and make your code more efficient? Well, you’re in luck! In this article, we’ll show you how to implement validation only once for properties and commands, and revolutionize the way you approach input validation in your applications.

Understanding the Problem

However, writing validation code for each property and command individually can be a daunting task. It’s not only time-consuming but also prone to errors and inconsistencies. Imagine having to write separate validation logic for each property and command, only to end up with duplicated code and a maintenance nightmare.

The Solution: Implementing Validation Only Once

Luckily, there’s a better way to approach input validation. By using a combination of design patterns and clever coding techniques, you can implement validation only once for properties and commands. This approach not only simplifies your code but also makes it more efficient, scalable, and maintainable.

Step 1: Define a Validation Interface

The first step is to define a validation interface that outlines the common validation methods and properties. This interface will serve as a contract for all validators to implement.

public interface IValidator<T>
{
    bool IsValid(T value);
    IEnumerable<ValidationResult> Validate(T value);
}

This interface consists of two methods: `IsValid` and `Validate`. The `IsValid` method returns a boolean indicating whether the input value is valid, while the `Validate` method returns a list of `ValidationResult` objects containing detailed information about the validation errors.

Step 2: Implement the Validator

Next, create a concrete implementation of the `IValidator` interface for each property and command. This implementation should contain the actual validation logic specific to the property or command.

public class UserNameValidator : IValidator<string>
{
    public bool IsValid(string value)
    {
        return !string.IsNullOrWhiteSpace(value) && value.Length > 3;
    }

    public IEnumerable<ValidationResult> Validate(string value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            yield return new ValidationResult("Username is required.");
        }
        else if (value.Length <= 3)
        {
            yield return new ValidationResult("Username must be at least 3 characters long.");
        }
    }
}

In this example, the `UserNameValidator` class implements the `IValidator` interface and provides custom validation logic for usernames.

Step 3: Create a Validator Factory

To simplify the process of creating and retrieving validators, create a validator factory class. This class will be responsible for instantiating and caching validators for each property and command.

public class ValidatorFactory
{
    private readonly Dictionary<Type, IValidator> _validators = new Dictionary<Type, IValidator>();

    public IValidator GetValidator<T>()
    {
        if (!_validators.TryGetValue(typeof(T), out IValidator validator))
        {
            validator = CreateValidator<T>();
            _validators.Add(typeof(T), validator);
        }
        return validator;
    }

    private IValidator CreateValidator<T>()
    {
        // Use reflection or other mechanisms to create an instance of the validator
        // For example:
        return (IValidator)Activator.CreateInstance(typeof(UserNameValidator));
    }
}

This factory class uses a dictionary to cache validators for each type, and provides a `GetValidator` method to retrieve the corresponding validator instance.

Step 4: Integrate with Properties and Commands

Now, integrate the validators with your properties and commands. You can do this by injecting the validator factory into your property or command classes.

public class User
{
    private readonly ValidatorFactory _validatorFactory;

    public User(ValidatorFactory validatorFactory)
    {
        _validatorFactory = validatorFactory;
    }

    public string Username
    {
        get { return _username; }
        set
        {
            if (!_validatorFactory.GetValidator<string>().IsValid(value))
            {
                throw new ValidationException("Invalid username.");
            }
            _username = value;
        }
    }
}

In this example, the `User` class takes a `ValidatorFactory` instance in its constructor and uses it to validate the `Username` property.

Benefits of Implementing Validation Only Once

By implementing validation only once for properties and commands, you can enjoy the following benefits:

• Reduced Code Duplication: With a centralized validation mechanism, you can avoid writing duplicated code for each property and command.
• Improved Code Maintainability: When changes are needed, you can update the validation logic in one place, without affecting the entire application.
• Enhanced Code Reusability: Validators can be reused across multiple properties and commands, reducing the overall codebase.
• Simplified Error Handling: With a standardized validation interface, error handling becomes more straightforward and consistent.

Common Pitfalls to Avoid

When implementing validation only once, be mindful of the following common pitfalls:

Pitfall	Description
Over-Engineering	Avoid over-engineering the validation mechanism, making it too complex or rigid.
Under-Engineering	Don’t underestimate the complexity of the validation requirements, leading to incomplete or inaccurate validation.
Performance Overhead	Be cautious of performance overhead introduced by the validation mechanism, especially in high-traffic applications.

Conclusion

In conclusion, implementing validation only once for properties and commands is a powerful technique to simplify and streamline input validation in your applications. By following the steps outlined in this article, you can create a more efficient, scalable, and maintainable validation mechanism that meets the unique requirements of your application.

Remember to keep your validation logic concise, flexible, and well-documented, and don’t hesitate to adapt and refine your approach as your application evolves.

Additional Resources

For further reading and learning, we recommend the following resources:

• ASP.NET Core MVC Model Validation
• Validation in .NET Core
• Validation Example GitHub Repository

By mastering the art of implementing validation only once, you’ll be well on your way to building robust, reliable, and user-friendly applications that delight your users and set your development team up for success.

Happy coding!

Frequently Asked Question

Are you tired of implementing validation for your properties and commands repeatedly? Here are some common questions and answers to help you implement validation only once!