[Solved] ASP.Net Error: Fill: SelectCommand.Connection property has not been initialized

 I have getting mntion error.

Error occured: Fill: SelectCommand.Connection property has not been initialized.

        protected void btnSendMail_Click(object sender, EventArgs e)
        {
            string Id = string.Empty;
            DataTable dt = new DataTable();
            try
            {
                foreach (GridViewRow row in GridView1.Rows)
                {
                    //get Current EMAIL_ID from the DataKey
                    Id = Convert.ToString(GridView1.DataKeys[row.RowIndex].Value);
                    CheckBox cb = (CheckBox)row.FindControl("chkSelect");
                    string flag = cb.Checked ? "Y" : "N";
                    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
                    using (SqlConnection con = new SqlConnection(constr))
                    {
                        SqlCommand cmd = new SqlCommand("UPDATE MESSAGE_SYSTEM SET flag = @flag where Id=@Id");
                        cmd.Connection = con;
                        cmd.Parameters.AddWithValue("@flag", flag);
                        cmd.Parameters.AddWithValue("@Id", Id);
                        con.Open();
                        string isUpdated = Convert.ToString(cmd.ExecuteNonQuery());
                        con.Close();
                    }
                    if (cb.Checked)
                    {
                        SqlCommand cmd = new SqlCommand("select VEN_EMP_EMAIL,EIC_MAIL_ID, PARTICULARS, REF_NO,AMT, VEN_EMP_PHNO, EIC_PH_NO from MESSAGE_SYSTEM where Id=" + Id + "", con);
                        SqlDataAdapter adp = new SqlDataAdapter(cmd);
                        //Fill datatable with EMAIL_ID corresponding to Current EMP_ID
                        adp.Fill(dt);
                        //Get EMAIL_ID into variable
                        string emailId = dt.Rows[0]["VEN_EMP_EMAIL"].ToString();
                        string emailId1 = dt.Rows[0]["EIC_MAIL_ID"].ToString();
                        string PARTICULARS = dt.Rows[0]["PARTICULARS"].ToString();
                        string AMT = dt.Rows[0]["AMT"].ToString();
                       
                        string REF_NO = dt.Rows[0]["REF_NO"].ToString();
                        string[] num = REF_NO.Split('&').Select(n => (n.Trim())).ToArray();
                        string phoneNo = dt.Rows[0]["VEN_EMP_PHNO"].ToString();
                        string phoneNo1 = dt.Rows[0]["EIC_PH_NO"].ToString();
                        //write code to send mail
                       // string message = "$#%^&*()?/|";

                        SendEmailUsingGmail(emailId, PARTICULARS, AMT, REF_NO);
                        SendEmailUsingGmail(emailId1, PARTICULARS, AMT, REF_NO);

                        sendSMS(phoneNo.Trim(), "Amount of Rs " + AMT + " for " + PARTICULARS + "  is sent to your Bank account against  "+ REF_NO +"  ");
                        sendSMS(phoneNo1.Trim(), "Amount of Rs " + AMT + " for " + PARTICULARS + " is sent to your Bank account against " + REF_NO + "  ");
                        dt.Clear();
                        dt.Dispose();
                    }
                }
                // ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), Guid.NewGuid().ToString(), "alert('Payment Details Sent Successfully');", true);
            }
            catch (Exception ex)
            {
                Response.Write("Error occured: " + ex.Message.ToString());
            }
            finally
            {
                Id = string.Empty;
            }

            System.Threading.Thread.Sleep(5000);
        }