LINQ to Entities does not recognize the method 'System.String ToString()'

Question

Hi, i am working on MVC using LINQ query where i am heading a problem with LINQ Query. When I use following code 
public ActionResult GetProduct()
Category p = new Category();
var all = db.Products.ToList();
// var catname = from i in db.Categories select i.CategoryID.ToString();
p.CategName = (from i in db.Categories select new SelectListItem {Value =i.CategoryID.ToString(), Text = i.CategoryName }).ToList();
var qq = (from i in db.Products join j in db.Categories on i.CategoryID equals j.CategoryID select new Product { ProductName = i.ProductName, UnitPrice = i.UnitPrice, UnitsOnOrder = i.UnitsOnOrder }).ToList();
p.Products = qq;
return View("GetProduct", p);
It throws an error
LINQ to Entities does not recognize the method 'System.String ToString(Int32)' method, and this method cannot be translated into a store expression.
kindly help to fix this problem.
Mayank Mani Pandey India

Answer 1

Entity Framework cannot convert ToString() to SQL. Create the object after you have fetched the results:
public ActionResult GetProduct()
Category p = new Category();
var all = db.Products.ToList();
// var catname = from i in db.Categories select i.CategoryID.ToString();
p.CategName = (from i in db.Categories select i).AsEnumerable().Select(x => new SelectListItem { Value = x.CategoryID.ToString(), Text = x.CategoryName }).ToList();
var qq = (from i in db.Products join j in db.Categories on i.CategoryID equals j.CategoryID select new Product { ProductName = i.ProductName, UnitPrice = i.UnitPrice, UnitsOnOrder = i.UnitsOnOrder }).ToList();
p.Products = qq;
return View("GetProduct", p);
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