How to retain the checkbox checked state in Gridview PageIndexChanging using ASP.Net?

How to retain the checkbox checked state in Gridview PageIndexChanging using ASP.Net?



List<int> arrSelectedItems; 

 protected void Page_Load(object sender, EventArgs e)
        {
             
                  arrSelectedItems = new List<int>();
              
        }

 protected void gvProductName_PageIndexChanging(object sender, GridViewPageEventArgs e)
        {
            try
            {
                SaveCheckBoxState(); 
                gvProductName.PageIndex = e.NewPageIndex;
               
                if (ViewState["BindData"] != null)
                {
                    DataTable dtProduct = (DataTable)ViewState["BindData"];
                    gvProductName.DataSource = dtProduct;
                    gvProductName.DataBind(); 
                }

            }
            catch (Exception ex)
            {
                
            }
        }

private void SaveCheckBoxState()
        {
            if (arrSelectedItems != null)
            {
                if (ViewState["SaveState"] != null)
                {
                    arrSelectedItems = (List<int>)ViewState["SaveState"];
                }
                foreach (GridViewRow item in gvProductName.Rows)
                {
                    try
                    {
                        if (item.RowType == DataControlRowType.DataRow)
                        {
                            CheckBox chk = (CheckBox)(item.Cells[0].FindControl("chkSelect"));
                            if (chk.Checked)
                            {
                                if (!arrSelectedItems.Contains(Convert.ToInt32(gvProductName.DataKeys[item.RowIndex].Values["Product_Id"].ToString())))
                                    arrSelectedItems.Add(Convert.ToInt32(gvProductName.DataKeys[item.RowIndex].Values["Product_Id"].ToString()));
                            }
                            else
                            {
                                if (arrSelectedItems.Contains(Convert.ToInt32(gvProductName.DataKeys[item.RowIndex].Values["Product_Id"].ToString())))
                                    arrSelectedItems.Remove(Convert.ToInt32(gvProductName.DataKeys[item.RowIndex].Values["Product_Id"].ToString()));
                            }
                        }
                        ViewState["SaveState"] = arrSelectedItems;
                    }
                    catch (Exception ex)
                    {
                        
                    }
                }
            }
        }

        protected void gvProductName_PreRender(object sender, EventArgs e)
        {
            try
            {
                if (arrSelectedItems != null)
                {
                    arrSelectedItems = (List<int>)ViewState["SaveState"];
                    foreach (GridViewRow item in gvProductName.Rows)
                    {
                        if (item.RowType == DataControlRowType.DataRow)
                        {
                            CheckBox chkbox = (CheckBox)item.FindControl("chkSelect");
                            if (arrSelectedItems != null)
                            {
                                if (arrSelectedItems.Contains(Convert.ToInt32(gvProductName.DataKeys[item.RowIndex].Values["Product_Id"].ToString())))
                                {
                                    chkbox.Checked = true;
                                }
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                
            }
        }