give custom validation in controller action method in aspmvc

Question

I am doing validation in controller part action method and I got stuck at a point that to give validation for name by checking the condition that the name should not appear already in the table. I have tried many conditions but always getting some error. can anyone please help me to find solution for my problem ???

 

controller

 

[HttpPost]

[ValidateAntiForgeryToken]

public async Task<ActionResult> Create([Bind(Include = "Id,Name")] Student student)

{

TempData["name"] = student.Name;

 

var show = db.Students.Select(e => e.Name).ToList();

if (show == TempData["name"])

{

ModelState.AddModelError("Name", "Name already exists");

}

 

f (ModelState.IsValid)

{

db.Students.Add(student);

await db.SaveChangesAsync();

return RedirectToAction("Index");

}

return View(student);

}

 

this is my controller part where I nned to give validation