I'm updating an integer value with a checkbox.

//this is my my business logic
public class CastVote
    {
       public Int32 id { get; set; }
       public Int32  [] cast { get; set; }
        
       public CastVote()
       {
       id=0;
       cast=null;
       }

       public CastVote(Int32 _id, int [] _cast) 
       {
           id = _id;
           cast = _cast;
       }

       public void Votes(Int32 id) 
       {
           csDAL objdal = new csDAL();
           List<csParameterListType> objlist = new List<csParameterListType>();
           objlist.Add(new csParameterListType("@id", System.Data.SqlDbType.Int, id));
           objdal.executespreturnnd("cast_vote", objlist);
       }
    }

//code behind the button
                StringCollection idCollection = new StringCollection();
                string  strid = string .Empty ;
                //loop through gridview to find checked rows
                for (int i = 0; i < GridView1.Rows.Count; i++) 
                {
                    CheckBox chckupdate = (CheckBox)GridView1.Rows[i].Cells[0].FindControl("chckhere");
                    if (chckupdate != null) 
                    {
                        if (chckupdate.Checked)
                        {
                            strid = GridView1.Rows[i].Cells[1].Text;
                            idCollection.Add(strid);
                        }
                    }
                }
                if (idCollection.Count >= 0)
                {
                    BLL.CastVote obj = new CastVote();
                    obj.id = Convert.ToInt32(idCollection.Count);
                    obj.Votes(); 
                   //it give an error here
               
                }
                else 
                {
                    //lblmsg.Text = "Please select your favourate candidates";
                }
            }