why we use this code in mvc entity framewirk

Question

// GET: /Student/Create
public ActionResult Create()
{
return View();
}
//
// POST: /Student/Create
[HttpPost] [ValidateAntiForgeryToken]
public ActionResult Create(Student student)
{
if (ModelState.IsValid)
{
db.Students.Add(student);
db.SaveChanges();
return RedirectToAction( "Index" );
}
return View(student);
}
//
what is meant by model state.isvalid why we check before to add student.
and why we use save changes() method here?

Rajkiran Swain · Answer

https://www.codeproject.com/Articles/695850/Complete-CRUD-Operations-in-MVC?fid=1849414&df=90&mpp=25&sort=Position&view=Topic&spc=Compact&fr=51

Abhishek Sharma · Answer

ModelState.IsValid tells you if any model errors have been added to ModelState . The default model binder will add some errors for basic type conversion issues (for example, passing a non-number for something which is an "int"). You can populate ModelState more fully based on whatever validation system you're using. The sample DataAnnotations model binder will fill model state with validation errors taken from the DataAnnotations attributes on your model.  I am not sure what do you mean whe you say " why we use save changes() method here? ".  But far as I understand, you can have it anywhere you want. Just make sure of initializing the Entity Framework DB context, add your row to the desired entity and save the changes using SaveChanges Entity Framework method.