The ASP.NET provides validation related tag helpers which display the validation messages to the user. We learned how server-side model validation works in the previous tutorial. The Model binder binds and validates the data received over the HTTP Request. It then creates the ModelState object, which contains the validation messages generated by the Model Binder. The Validation Tag helpers generate the HTML element to display these messages in the view.
In this tutorial, we look at how ASP.NET core Model Validation works. Often the data entered by the user is not valid and cannot be saved into the database. The entered data may contain a typo or user may intentionally enter the inappropriate data. Hence, we need to validate the user input before storing it in the database. The ASP.NET Core gives us Model Validator, which uses the validation attributes to validate the model, which makes our task easier. We also take a look at ModelState and how to use it. Finally, we look at the list of Validation attributes.