i am using code first method , i need to bind a dropdown using repositry , viewmodel

i have a viewmodel Infoviewmodel where i need to populate the dropdown from tblstates as per country selected

i have created a Repository DropDownList Repository on Repository folder

DropDownList.cs has the below code

               public List<SelectListItem> GetstateList(int countryId)
               {
                   var statelist = (from p in db.state
                                  where (p.stateId == stateId)
                                     select new SelectListItem
                                         {
                                                Text = p.state,
                                                Value = p.stateID.ToString() 
                                         });

                   return statelist.ToList();
 
              }

viewmodel

    public class infoviewmodel
    {
        [Key]
        public int stateID { get; set; }
        public string stateName { get; set; }
       public virtual state state{get;set;}
       public string ddlstate
       {
           get;
           set;
       }
                                  //DropDownList Values
      public List<SelectListItem> StateValue
      {
         get;
        set;
       }
    }

controller

      //Creating an instance of infoviewmodel 
            infoviewmodel objinfoviewmodel = new infoviewmodel();
            objinfoviewmodel.StateValue = objRepository.GetstateList(1);
            
            
            return View(objinfoviewmodel);
        }

state model

public class state
{
        public int stateID { get; set; }

       [StringLength(50, ErrorMessage = "state name cannot be greater than 50 characters.")]
       [Display(Name = "state Name")]
        public string stateName { get; set; }

        public int? countryId { get; set; }
        //[ForeignKey("countryId")]
        public virtual Country Country { get; set; }
}

i am not able to create view using the viewmodel

error

There was an error running the selected code generator: 'Unable to retrieve metadata for 'Application1.ViewModels.infoviewmodel'. One or more validation errors were detected during model generation:

SelectListItem: : EntityType 'SelectListItem' has no key defined. Define the key for this EntityType. SelectListItems: EntityType: EntitySet 'SelectListItems' is based on type 'SelectListItem' that has no keys defined.

is the above method a correct way ? or is there any best method