System.invalidoperationexception sequence contains no elements openxml

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C#

SQL

OpenXML

I am getting some Exception errors using OpenXML to populate data from MSSQL server on a content control. I want to do a simple walk around to have the data populated from a table in the Database and print on an MS Word Document, and I am using the OpenXML SDK.

Having compiled the program and run to see what happens, I am getting this exception error : system.invalidoperationexception Sequence contains no elements

My code looks somewhat like this

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Wordprocessing;
using DocumentFormat.OpenXml.Drawing;
using System.Data.SqlClient;
using System.IO;

namespace DesktopSignaturetest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string constring = @"Data Source=DESKTOP-9CM4N5S\SQLEXPRESS;Initial Catalog=SignatureBox2;User ID=sa;Password=123456;";
            using (SqlConnection con = new SqlConnection(constring))
            {
                con.Open();
                string q = "select * from SignatureBox_DB where StaffID = @StaffID";
                using (SqlCommand cmd = new SqlCommand(q, con))
                {
                    cmd.Parameters.AddWithValue("@StaffID", textBox1.Text);
                    using (SqlDataReader rd = cmd.ExecuteReader())
                    {
                        try
                        {
                            if (rd.Read())
                            {
                                string fileName = @"C:\Users\emi\Desktop\test.jpg";
                                byte[] imageBytes = Convert.FromBase64String(rd["SignatureBase64"].ToString());
                                string fullname = rd["FullName"].ToString();
                                string designation = rd["Designation"].ToString();
                                MemoryStream ms = new MemoryStream(imageBytes, 0, imageBytes.Length);
                                ms.Write(imageBytes, 0, imageBytes.Length);
                                Image image = Image.FromStream(ms, true, true);
                                image.Save(fileName, System.Drawing.Imaging.ImageFormat.Jpeg);

                                using (WordprocessingDocument doc = WordprocessingDocument.Open(@"C:\Users\emi\Desktop\MSWordTest.docx", true))
                                {
                                    MainDocumentPart mainPart = doc.MainDocumentPart;
                                    SdtBlock block = mainPart.Document.Body.Descendants<SdtBlock>().Where
                                    (r => r.SdtProperties.GetFirstChild<Tag>().Val == "Name").Single();

                                    SdtBlock desg = mainPart.Document.Body.Descendants<SdtBlock>().Where
                                    (r => r.SdtProperties.GetFirstChild<Tag>().Val == "Designation").Single();


                                    SdtBlock cc = doc.MainDocumentPart.Document.Body.Descendants<SdtBlock>()
                                    .FirstOrDefault(c =>
                                    {
                                        SdtProperties p = c.Elements<SdtProperties>().FirstOrDefault();
                                        if (p != null)
                                        {
                                            // Is it a picture content control?
                                            SdtContentPicture pict =
                                                p.Elements<SdtContentPicture>().FirstOrDefault();
                                            // Get the alias.
                                            SdtAlias a = p.Elements<SdtAlias>().FirstOrDefault();
                                            if (pict != null && a.Val == "Signature")
                                                return true;
                                        }
                                        return false;
                                    });

                                    string embed = null;
                                    if (cc != null)
                                    {
                                        Drawing dr = cc.Descendants<Drawing>().FirstOrDefault();
                                        if (dr != null)
                                        {
                                            Blip blip = dr.Descendants<Blip>().FirstOrDefault();
                                            if (blip != null)
                                                embed = blip.Embed;
                                        }
                                    }
                                    if (embed != null)
                                    {
                                        IdPartPair idpp = doc.MainDocumentPart.Parts
                                            .Where(pa => pa.RelationshipId == embed).FirstOrDefault();
                                        if (idpp != null)
                                        {
                                            DocumentFormat.OpenXml.Drawing.Text name = block.Descendants<DocumentFormat.OpenXml.Drawing.Text>().Single();
                                            DocumentFormat.OpenXml.Drawing.Text desgx = desg.Descendants<DocumentFormat.OpenXml.Drawing.Text>().Single();
                                            name.Text = fullname;
                                            desgx.Text = designation;
                                            ImagePart ip = (ImagePart)idpp.OpenXmlPart;
                                            using (FileStream fileStream =
                                                File.Open(fileName, FileMode.Open))
                                                ip.FeedData(fileStream);
                                            MessageBox.Show("Done!");
                                        }
                                    }
                                }
                            }
                        }
                        catch (Exception ex)
                        {
                            MessageBox.Show(ex.ToString());
                        }
                        finally
                        {
                            con.Close();
                        }
                    }
                }
            }
        }
    }
}

What I have tried:

The code fires an Exception error here

SdtBlock block = mainPart.Document.Body.Descendants<SdtBlock>().Where
(r => r.SdtProperties.GetFirstChild<Tag>().Val == "Name").Single();

Please what am i getting wrong?