Error: LINQ to Entities does not recognize method 'Int32 ToInt32

I want to convert string to int in linq query and get the following error

Error: LINQ to Entities does not recognize method 'Int32 ToInt32

DataBase Filed arID contains varchar

var AllArea = (from arr in dbcontext.Areas
               join city in dbcontext.Cities on Convert.ToInt32(arr.arID) equals city.cityID
               select new
               {
                   arr.arID,
                   arr.AreaName,
                   city.cityID,
                   city.cityName
               }).ToList();