How do I implement validation logic in my MVC app?

How do I implement validation logic in my MVC app?

You can implement validation logic in your MVC app using data annotations or custom validation attributes. Would you like examples?

Yes, please provide examples of both data annotations and custom validation.

For data annotations, you can use attributes like [Required] or [StringLength]. For custom validation, create a class that implements IValidatableObject.

Can you show me a code snippet for a custom validation attribute?

Sure! Here's a simple example:

public class AgeValidationAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value is int age && age < 18)
        {
            return new ValidationResult("Age must be 18 or older.");
        }
        return ValidationResult.Success;
    }
}