HttpContext data caching in entity framework

Question

I am trying to cache an entity using HttpContext caching. My code in service layer is as follows

public Product GetById(long id)
{
  Product product;
  string storageKey = string.Format("products_{0}",id.ToString());
  product = (Product)HttpContext.Current.Cache.Get(storageKey);
  if (product == null)
  {
     product = _productContext.Products.Find(id);
      HttpContext.Current.Cache.Insert(storageKey, product);
  }     
  return product;
}

and using in client like this:

 ProductService productServices = new ProductService(_dbContext);
 var product = productServices.GetById(id);
  //... Populating controls

 //On Update button click
  ProductService productServices = new ProductService(_dbContext);
  var product = productServices.GetById(id);
  //Updating values of product and saveChanges.

While getting the item it is working fine. But when i try to save the item after updating it getting this error:

An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

I understand this is due to retrieving and updating using different DbContexts. When using without caching its working fine. Is there any better other methods to do caching in entity framework ?

Answer 1

Try to attach cached product to current context:

public Product GetById(long id)
{
   Product product;
   string storageKey = string.Format("products_{0}",id.ToString());
   product = (Product)HttpContext.Current.Cache.Get(storageKey);
   if (product == null)
   {
      product = _productContext.Products.Find(id);
      HttpContext.Current.Cache.Insert(storageKey, product);
   }
   else
   {
       _productContext.Products.Attach(product);
   }
   return product;
}

Also if you are using Asp.Net MVC then consider to use output caching to cache content returned by controller action.