Скачать или смотреть How to Make Custom Validation in Asp.Net MVC 5

Validation in ASP.NET MVC 5 is a process of checking user input to ensure that it meets specific criteria or requirements. It is an essential part of building secure and reliable web applications that provide a good user experience.

ASP.NET MVC 5 provides built-in validation features that enable developers to easily validate user input without writing a lot of custom code. These features include data annotations, which are attributes that can be applied to model properties to specify validation rules, and validation helpers, which can be used to generate client-side validation scripts and display validation error messages.

Using data annotations, developers can specify requirements such as required fields, minimum and maximum length, and regular expression patterns that user input must match. The validation helpers can then generate client-side validation scripts that provide real-time feedback to users as they fill out forms, highlighting errors and providing helpful error messages.

ASP.NET MVC 5 also provides server-side validation, which can be used to validate user input after it has been submitted to the server. This can be useful for more complex validation rules that cannot be easily checked on the client side.

In summary, validation in ASP.NET MVC 5 helps ensure that user input is accurate and meets the required criteria, providing a better user experience and improving the overall security and reliability of web applications.