Hiamar,

Refer below sample code for sending multiple attachment of binary data from database.

Send email with multiple attachments using Multiple FileUpload control in ASP.Net 4.5

C#

protected void SendEmail(object sender, EventArgs e)
{
    string to = txtTo.Text;
    string from = txtEmail.Text;
    string subject = txtSubject.Text;
    string body = txtBody.Text;
    using (MailMessage mm = new MailMessage(txtEmail.Text, txtTo.Text))
    {
        mm.Subject = txtSubject.Text;
        mm.Body = txtBody.Text;
        foreach (DataRow dr in GetFileFromDataBase().Rows)
        {
            mm.Attachments.Add(new Attachment(new MemoryStream((byte[])dr["Data"]), dr["Name"].ToString()));
        }
        mm.IsBodyHtml = false;
        SmtpClient smtp = new SmtpClient();
        smtp.Host = "smtp.gmail.com";
        smtp.EnableSsl = true;
        NetworkCredential NetworkCred = new NetworkCredential(txtEmail.Text, txtPassword.Text);
        smtp.UseDefaultCredentials = true;
        smtp.Credentials = NetworkCred;
        smtp.Port = 587;
        smtp.Send(mm);
        ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Email sent.');", true);
    }
}

private DataTable GetFileFromDataBase()
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    string query = "SELECT * FROM tblFiles";
    SqlCommand cmd = new SqlCommand(query);
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            using (DataTable dt = new DataTable())
            {
                sda.Fill(dt);
                return dt;
            }
        }
    }
}

VB.Net

    Protected Sub SendEmail(ByVal sender As Object, ByVal e As EventArgs)
        Dim [to] As String = txtTo.Text
        Dim from As String = txtEmail.Text
        Dim subject As String = txtSubject.Text
        Dim body As String = txtBody.Text

        Using mm As MailMessage = New MailMessage(txtEmail.Text, txtTo.Text)
            mm.Subject = txtSubject.Text
            mm.Body = txtBody.Text

            For Each dr As DataRow In GetFileFromDataBase().Rows
                mm.Attachments.Add(New Attachment(New MemoryStream(CType(dr("Data"), Byte())), dr("Name").ToString()))
            Next

            mm.IsBodyHtml = False
            Dim smtp As SmtpClient = New SmtpClient()
            smtp.Host = "smtp.gmail.com"
            smtp.EnableSsl = True
            Dim NetworkCred As NetworkCredential = New NetworkCredential(txtEmail.Text, txtPassword.Text)
            smtp.UseDefaultCredentials = True
            smtp.Credentials = NetworkCred
            smtp.Port = 587
            smtp.Send(mm)
            ClientScript.RegisterStartupScript(Me.[GetType](), "alert", "alert('Email sent.');", True)
        End Using
    End Sub

    Private Function GetFileFromDataBase() As DataTable
        Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Dim query As String = "SELECT * FROM tblFiles"
        Dim cmd As SqlCommand = New SqlCommand(query)
        Using con As SqlConnection = New SqlConnection(conString)
            Using sda As SqlDataAdapter = New SqlDataAdapter()
                cmd.Connection = con
                sda.SelectCommand = cmd
                Using dt As DataTable = New DataTable()
                    sda.Fill(dt)
                    Return dt
                End Using
            End Using
        End Using
    End Function