How to upload and download files using database in C#.NET windows application?

using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Diagnostics;

namespace FileUploadWindows
{
    public partial class Form1 : Form
    {
        SqlConnection sqlcon = new SqlConnection(@"Data Source=.\SQlEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True");
        SqlCommand sqlcmd = new SqlCommand();
        SqlDataAdapter da = new SqlDataAdapter();
        DataTable dt = new DataTable();
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            LoadGrid();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog fDialog = new OpenFileDialog();
            fDialog.Title = "Select file to be upload";
            //fDialog.Filter = "PDF Files|*.pdf|All Files|*.*";
            fDialog.Filter = "PDF Files|*.pdf";
            if (fDialog.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = fDialog.FileName.ToString();
            }
        }

        void LoadGrid()
        {
            dataGridView1.Columns.Clear();
            sqlcon.Open();
            sqlcmd = new SqlCommand("select ID,fname from PDFupload", sqlcon);
            da = new SqlDataAdapter(sqlcmd);
            dt = new DataTable();
            da.Fill(dt);
            sqlcon.Close();
            if (dt.Rows.Count>0)
            {
                DataGridViewLinkColumn links = new DataGridViewLinkColumn();
                links.UseColumnTextForLinkValue = true;
                links.HeaderText = "Download";
                links.DataPropertyName = "lnkColumn";
                links.ActiveLinkColor = Color.White;
                links.LinkBehavior = LinkBehavior.SystemDefault;
                links.LinkColor = Color.Blue;
                links.Text = "Click here";
                links.TrackVisitedState = true;
                links.VisitedLinkColor = Color.YellowGreen;
                dataGridView1.Columns.Add(links);                
                dataGridView1.DataSource = dt;

                dataGridView1.AutoResizeColumns();
            }    
        }

        private void button2_Click(object sender, EventArgs e)
        {
            string filetype;
            string filename;

            filename=textBox1.Text.Substring(Convert.ToInt32(textBox1.Text.LastIndexOf("\\"))+1,textBox1.Text.Length - (Convert.ToInt32(textBox1.Text.LastIndexOf("\\"))+1));
            filetype=textBox1.Text.Substring(Convert.ToInt32(textBox1.Text.LastIndexOf("."))+1,textBox1.Text.Length - (Convert.ToInt32(textBox1.Text.LastIndexOf("."))+1));

            //Validate user upload only specific bytes - un comment below lines if you need to validate only PDF files

            if (filetype.ToUpper() != "PDF")
            {
                MessageBox.Show("Upload Only PDF Files");
                return;
            }

            byte[] FileBytes = null;

            try
            {
                // Open file to read using file path
                FileStream FS = new FileStream(textBox1.Text, System.IO.FileMode.Open, System.IO.FileAccess.Read);

                // Add filestream to binary reader
                BinaryReader BR= new BinaryReader(FS);

                // get total byte length of the file
                long allbytes = new FileInfo(textBox1.Text).Length;

                // read entire file into buffer
                FileBytes = BR.ReadBytes((Int32)allbytes);

                // close all instances
                FS.Close();
                FS.Dispose();
                BR.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error during File Read " + ex.ToString());
            }

            //Store File Bytes in database image filed 

            sqlcon.Open();
            SqlCommand sqlcmd = new SqlCommand("insert into PDFupload(fname,fcontent) values (@FN, @FB)", sqlcon);
            sqlcmd.Parameters.AddWithValue("@FN", filename);
            sqlcmd.Parameters.AddWithValue("@FB", FileBytes);           
            sqlcmd.ExecuteNonQuery();
            sqlcon.Close();
            LoadGrid();
        }

        private void dataGridView1_CellContentDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            
        }

        //Below code is used to open Your stored PDF 
        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == 0)
            {
                string id;
                FileStream FS = null;
                byte[] dbbyte;

                //Get selected file ID field
                id = dataGridView1.Rows[e.RowIndex].Cells[1].Value.ToString();

                sqlcon.Open();
                sqlcmd = new SqlCommand("select * from PDFupload where ID='" + id + "'", sqlcon);
                da = new SqlDataAdapter(sqlcmd);
                dt = new DataTable();
                da.Fill(dt);
                sqlcon.Close();


                if (dt.Rows.Count > 0)
                {
                    //Get a stored PDF bytes
                    dbbyte = (byte[])dt.Rows[0]["fcontent"];

                    //store file Temporarily 
                    string filepath = "D:\\temp.pdf";


                    //Assign File path create file
                    FS = new FileStream(filepath, System.IO.FileMode.Create);

                    //Write bytes to create file
                    FS.Write(dbbyte, 0, dbbyte.Length);

                    //Close FileStream instance
                    FS.Close();


                    // Open fila after write 

                    //Create instance for process class
                    Process Proc = new Process();

                    //assign file path for process
                    Proc.StartInfo.FileName = filepath;
                    Proc.Start();
                }
                sqlcon.Close();
            }
        }        
    }
}