Unable to edit rows in grid with checkbox

I have a grid where I use a checkbox for bulk update by selecting multiple rows. Now the footer template with the textbox , assume like I select two rows in the grid(using checkbox) and when I enter values in the textbox in footertemplate below the grid, then changes have to be reflected to the selected rows in the grid for the columns(to the DB). And I use the below code for updating the grid wirh checkbox.

 protected void Save(object sender, EventArgs e)
        {
            foreach (GridViewRow row in GridView1.Rows)
            {
                if (row.RowType == DataControlRowType.DataRow)
                {
                    bool isChecked = row.Cells[0].Controls.OfType().FirstOrDefault().Checked;
                   if (isChecked)
                    {                      
                        SqlCommand cmd = new SqlCommand("UPDATE AppInvent_Test SET Name = @Name, Designation = @Designation, City = @City WHERE EmpID = @EmpID");
                        cmd.Parameters.AddWithValue("@EmpID", row.Cells[1].Controls.OfType().FirstOrDefault().Text);
                        cmd.Parameters.AddWithValue("@Name", row.Cells[2].Controls.OfType().FirstOrDefault().Text);
                        cmd.Parameters.AddWithValue("@Designation", row.Cells[3].Controls.OfType().FirstOrDefault().Text);
                        cmd.Parameters.AddWithValue("@City", row.Cells[4].Controls.OfType().FirstOrDefault().Text);
                        this.ExecuteQuery(cmd, "SELECT");
                    }
                }
            }
            this.FillVendorGrid();
        }