LINQ unable to update Record. it is

Question

var exist = db.Registration.FirstOrDefault(x => x.MOBILENUMBER == mobilenumber && x.EMAIL == email );

return exist;

 

 

while updating the record i need to check mobilenumbaer and email. with same id.  unable to update please help me out.

  ex : id =280 mnumber :9876545 name:David

         id =281 mnumber:890765    name:johnson

updating id=280  if i update name it is not getting updated it saying mobile number already exist.