What is the ModelState class in MVC 3?

Question

I am learning MVC, and in ASP.Net MVC 3, what is the ModelState class ? I have looked on Google and MSDN, but I can't seem to get a clear understanding of it's purpose. Can anyone help?

Answer 1

Take a look at http://www.gxclarke.org/2010/05/consumption-of-data-in-mvc2-views.html under the ViewData.ModelState section.

The ModelState property is a dictionary object that tracks HTTP values submitted to the server. In addition to storing the name and value of each field, it also tracks associated validation errors. Although its name may suggest otherwise, ModelState isn’t Model-aware. It doesn’t understand what a "Product" is. It simply contains a collection of items with names such as "ProductName" and "UnitPrice". It is the responsibility of other objects—ModelBinders, ViewResult, and the strongly-typed View—to map and interpret ModelState values as Model properties

Answer 2

The ModelState Class in MVC is a class which contains the collection that has the key and values of the data submitted to server in the Post method.When MVC comes across the post it takes all the parameters in the post request and puts them in the instance of a ModelStateDictionary. Whenever the ModelState is active in server,the properties of the model are validated according to the validation attributes that are associated with them. And if any of the property is invalid it will be added to the error list. And the property ModelState.IsValid will be set to false. You can use this later on your code to check if everything is correct.

Refer this link for further information.