What are some examples of custom validation in ASP.NET?

What are some examples of custom validation in ASP.NET?

In ASP.NET, custom validation can be implemented using attributes or by creating a custom validation class. For example, you can create a custom attribute that checks if a string is a valid email address.

Can you show me a code example of a custom validation attribute?

Sure! Here's a simple example:

public class EmailValidationAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var email = value as string;
        if (!string.IsNullOrEmpty(email) && !email.Contains("@"))
        {
            return new ValidationResult("Invalid email address.");
        }
        return ValidationResult.Success;
    }
}

How do I apply this custom validation attribute to a model?

You can apply the custom validation attribute to a model property like this:

public class UserModel
{
    [EmailValidation]
    public string Email { get; set; }
}

What if I want to add multiple validation rules?

You can create multiple custom validation attributes and apply them to the same property, or you can combine logic within a single custom attribute to handle multiple rules.