How to retrieve selected checkbox values from database in asp.net

Do it on RowDataBound event of GridView.

protected void gv1_RowDataBound(object sender, GridViewRowEventArgs e)
{
  if (e.Row.RowType == DataControlRowType.DataRow)
  {
     CheckBox chk = (CheckBox)e.Row.FindControl("yourChekcBoxID");
     DataRowView drv = (DataRowView)e.Row.DataItem;

     chk.Checked = Convert.ToBoolean(drv["YourDataBaseField"]); 
  }
}

try below for 1 check box.

bool isChecked = (CheckBox)GridViewName.Rows.FindControl("chkBoxID")).Checked

Or

CheckBox ChkBox = (CheckBox)GridViewName.Rows.FindControl("chkBoxID")).value

try below methods for more than 1 check box

// Select the checkboxes from the GridView control
for (int i = 0; i < GridView1.Rows.Count; i++)
{
  GridViewRow row = GridView1.Rows[i];
  bool isChecked = ((CheckBox) row.FindControl("chkSelect")).Checked;

  if (isChecked)
  {
   
  }
}

Thanks,

firstly what r u storing in database when your check box is checked ,i mean tiny int or Boolean ,suppose u r storing as tiny int then u should try like this

Check on row data bound event

protected void gvHardware_RowDataBound(object sender, GridViewRowEventArgs e)
{
   if (e.Row.RowType == DataControlRowType.DataRow)
   {
      // find check box 
      CheckBox ChkBox = (CheckBox)GridViewName.Rows.FindControl("chkBoxID"));
      // Now check the column of data table according to that u will check or uncheck the grid check box 
      strCheck = ((DataRowView)e.Row.DataItem)["operation"].ToString();
      if(strCheck=="1")
      {
         ChkBox .Checked=true;
      }
   }
}

hope this will help u
Thanks