how to check already existing record in mvc

I am new to mvc and i am creating application with built in read/write controller and views using entity framework , below is my create customer controller now i want to check the unique mobile number i mean mobile number for each customer should be unique , how to check that below is my controller code.

[HttpPost]

[ValidateAntiForgeryToken]

public ActionResult Create([Bind(Include = "Cutomer_ID,Customer_Name,Phone,Location,Email,gender")] Customer customer, string BtnPrevious, string BtnNext)

{

// bool isexists = db.customers.Any(x => x.ContactId == _customer.ContactId)

if (ModelState.IsValid)

{

//bool contactExists = db.Customers.Any(contact => contact.Customer_Name.Equals());

db.Customers.Add(customer);

db.SaveChanges();

// return View("~/Views/Orders/Details.cshtml");

// return RedirectToAction("~/Views/Shirts/Index.cshtml");

}

return View(customer);

}

this did the job successfully

[HttpPost]

[ValidateAntiForgeryToken]

public ActionResult Create([Bind(Include = "Cutomer_ID,Customer_Name,Phone,Location,Email,gender")] Customer customer, string BtnPrevious, string BtnNext)

{

// bool isexists = db.Customers.Any(x => x.Email == customer.Email);

if (ModelState.IsValid)

{

bool isexists = db.Customers.Any(x => x.Email == customer.Email);

if(isexists)

{

ModelState.AddModelError("Email", "Email Address is already in use !");

return View();

}

//bool contactExists = db.Customers.Any(contact => contact.Customer_Name.Equals());

db.Customers.Add(customer);

db.SaveChanges();

// return View("~/Views/Orders/Details.cshtml");

return RedirectToAction("Index");

}

return View(customer);

}