public bool IsContactSerialNoExisting(bool isContactSerialNoExisting = false)
{
MarikinaOpticalEntities dbContext = new MarikinaOpticalEntities();
var contactSerialNo = dbContext.GetSerialNumberContactRx(txtSerialNo.Text);
foreach (var number in contactSerialNo)
{
isContactSerialNoExisting = true;
}
return(isContactSerialNoExisting);
}