How can I implement custom validation in MVC?

How can I implement custom validation in MVC?

You can create a custom validation attribute by inheriting from the ValidationAttribute class. Would you like a code example?

Yes, please provide a code example.

Sure! Here's a simple example:

public class CustomValidationAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value == null || value.ToString() != "ExpectedValue")
        {
            return new ValidationResult("Invalid value.");
        }
        return ValidationResult.Success;
    }
}

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

You can apply it like this:

public class MyModel
{
    [CustomValidation]
    public string MyProperty { get; set; }
}