c# - Entity Framework Winforms -

i have 2 controls on windows form - combobox , listbox.

i'm trying populate listbox based on selected value combobox, keep getting following error.

unable cast object of type 'system.data.entity.dynamicproxies.category_b0496327038cb6b25a6ef7b750129dd7b44a87be41c4e2db0f8d7a00898b060f' type 'system.iconvertible'.

public partial class form1 : form {     northwindentities dbcontext = new northwindentities();      public form1()     {         initializecomponent();     }      private void form1_load(object sender, eventargs e)     {         cbx_categories.datasource = dbcontext.categories.tolist();         cbx_categories.displaymember = "categoryname";         cbx_categories.valuemember = "categoryid";     }      private void cbx_categories_selectedindexchanged(object sender, eventargs e)     {         int categoryid = convert.toint16(cbx_categories.selectedvalue);         populateproductslbx(categoryid);     }      void populateproductslbx(int categoryid)     {         var products = p in dbcontext.products                        p.categoryid == categoryid                        select p.productname;          lbx_products.datasource = products.tolist();     } } 

what best approach resolve this? thank in advance.

have thought trying

int categoryid = ((datarowview)cbx_categories.selecteditem).row["categoryid"];

this should handle casting you.