一个RowUpdating事件问题

protected void dg_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        string  nid = dg.DataKeys[e.RowIndex].Value.ToString();
        string strUpdata = "update 银行帐户 set passwordchar='"+((TextBox)dg.Rows[0].Cells[3].Controls[0]).Text+"' where userid='"+nid+"'";
        SqlCommand cmd = new SqlCommand(strUpdata, conn);
        conn.Open();
        try
        {
            cmd.ExecuteNonQuery();
            Response.Write("更新成功");
            dg.EditIndex = -1;
            BindGridView();
        }
        catch (Exception ex)
        {
            Response.Write("更新失败" + ex.Message.ToString());
        }
        finally
        {
            conn.Close();
        }

    }

        {
            conn.Close();
        } 

出现这样的错误



请问如何解决