SqlConnection sqlConn = new SqlConnection("connection string");

 <form id="form1" runat="server">
   <table style="z-index: 103; left: 94px; position: absolute; top: 71px">
        <tr>
            <td>
                <input id="txtFileContents" type="file" runat="server" name="FileUpload"/>
            </td>
        </tr>
        <tr>
            <td align="right">
                <asp:button id="btnUpload" Text="Upload" Runat="server" OnClick="btnUpload_Click" ></asp:button> 
            </td>
        </tr>
   </table>
           
           
        <asp:GridView ID="gvFiles" runat="server" Style="z-index: 104; left: 90px; position: absolute;
            top: 150px" CellPadding="4" ForeColor="#333333" GridLines="None" OnSelectedIndexChanged="gvFiles_SelectedIndexChanged">
            <Columns>
                <asp:TemplateField ShowHeader="False">
                    <ItemTemplate >
                        <asp:LinkButton ID="lnkDownload" ForeColor="DarkOrange" runat="server" CausesValidation="False" CommandName="Select"
                            Text="Download"></asp:LinkButton>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
            <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
            <RowStyle BackColor="#EFF3FB" />
            <EditRowStyle BackColor="#2461BF" />
            <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
            <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
            <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
            <AlternatingRowStyle BackColor="White" />
        </asp:GridView>
    
     
    </form>

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            Fill();
        }
    }


 protected void btnUpload_Click(object sender, EventArgs e)
    {
        string strFileName = txtFileContents.PostedFile.FileName.Substring(txtFileContents.PostedFile.FileName.LastIndexOf("\\") + 1);
        string strFileType = txtFileContents.PostedFile.ContentType;
        int intFileLen = txtFileContents.PostedFile.ContentLength;
        Stream objStream = txtFileContents.PostedFile.InputStream;
        byte[] bytFile = new byte[intFileLen];
        objStream.Read(bytFile, 0, intFileLen);

        SqlCommand cmdUploadFile = new SqlCommand("sp_Files", sqlConn);
        cmdUploadFile.CommandType = CommandType.StoredProcedure;
        cmdUploadFile.Parameters.Add("@FileName ", SqlDbType.VarChar, 50);
        cmdUploadFile.Parameters.Add("@Files", SqlDbType.Image);
        cmdUploadFile.Parameters.Add("@FileType", SqlDbType.VarChar, 50);
        cmdUploadFile.Parameters[0].Value = strFileName;
        cmdUploadFile.Parameters[1].Value = bytFile;
        cmdUploadFile.Parameters[2].Value = strFileType;

        sqlConn.Open();
        cmdUploadFile.ExecuteNonQuery();
        sqlConn.Close();
        Fill();
    }


  protected void gvFiles_SelectedIndexChanged(object sender, EventArgs e)
    {
        string strId = gvFiles.SelectedRow.Cells[1].Text;
        SqlCommand cmd = new SqlCommand("select FileType,Files,FileName from Files where id=" + strId + "", sqlConn);
        sqlConn.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        while (dr.Read())
        {
           string strFileType = dr[0].ToString(); 
           string strFileName = dr[2].ToString();
           //if below statement is not there, it will not effect the operation
           Response.ContentType = strFileType;
           Response.AddHeader("content-disposition", "attachment;filename=" + strFileName + "");
           Response.BinaryWrite((byte[])dr[1]);
           Response.End();
           
        }
        sqlConn.Close();
    }


public void Fill()
    {
        SqlDataAdapter sdaFiles = new SqlDataAdapter("select id,FileType,Files,FileName from Files", sqlConn);
        DataSet dsFiles = new DataSet();
        sdaFiles.Fill(dsFiles);
        gvFiles.DataSource = dsFiles;
        gvFiles.DataBind();
    }