In a web application the domain classes and the validations associated with those classes forms the Model. Validation plays a core part in a Model. In ASP.NET MVC, model validations are done by using Data Annotations. Data Annotations are nothing but special attributes that are applied to a class or properties of a class. In many cases these built-in validation attributes are not sufficient to fulfill our business requirements and in those cases we can go for building our own custom validations.
In this article we will see how to apply basic validations to a model and also we will see how to create custom validations by implementing the ValidationAttribute class or IValidatableObject interface.