[Solved] Email attachment is Empty when sending to multiple Addresses using Parallel ForEach in ASP.Net

Hi shal,

Check this example. Now please take its reference and correct your code.

HTML

<asp:TextBox runat="server" ID="txtemailfrom" />
<asp:TextBox runat="server" ID="txtsubject" Text="Test Subject" />
<asp:TextBox runat="server" ID="txtbody" Text="Test Body" />
<asp:FileUpload ID="fileUploader" runat="server" />
<asp:Button Text="Save" runat="server" OnClick="OnSave" />

Namepsces

C#

using System.Data;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Mail;
using System.Threading.Tasks;

VB.Net

Imports System.Data
Imports System.IO
Imports System.Linq
Imports System.Net
Imports System.Net.Mail
Imports System.Threading.Tasks

Code

C#

protected void OnSave(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] { 
        new DataColumn("PERSONAL_EMAILID"), new DataColumn("ENAME"), new DataColumn("OFFICIAL_EMAILID") });
    dt.Rows.Add("test1@gmail.com", "Test 1", "test2@gmail.com");
    dt.Rows.Add("test3@gmail.com", "Test 2", "test4@gmail.com");

    Stream fs = fileUploader.PostedFile.InputStream;
    BinaryReader br = new BinaryReader(fs);
    byte[] bytes = br.ReadBytes((Int32)fs.Length);
    string fileName = Path.GetFileName(fileUploader.PostedFile.FileName);

    Parallel.ForEach(dt.AsEnumerable(), row =>
    {
        SendEmail(row["PERSONAL_EMAILID"].ToString(), txtsubject.Text, string.Format("{0}", row["ENAME"]), fileName, bytes);
        SendEmail(row["OFFICIAL_EMAILID"].ToString(), txtsubject.Text, string.Format("{0}", row["ENAME"]), fileName, bytes);
    });
}

private void SendEmail(string recipient, string subject, string body, string fileName, byte[] bytes)
{
    string from = txtemailfrom.Text;
    using (MailMessage mail = new MailMessage(from, recipient))
    {
        mail.Subject = subject;
        mail.Body = body;
        if (bytes.Length > 0)
        {
            mail.Attachments.Add(new Attachment(new MemoryStream(bytes), fileName));
        }

        mail.IsBodyHtml = false;
        SmtpClient smtp = new SmtpClient();
        smtp.Host = "smtp.gmail.com";
        smtp.EnableSsl = true;
        NetworkCredential networkCredential = new NetworkCredential(from, "password");
        smtp.UseDefaultCredentials = true;
        smtp.Credentials = networkCredential;
        smtp.Port = 25;
        smtp.Send(mail);
        ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", "alert('Message has been sent successfully.');window.location ='SendBulkMail.aspx';", true);
    }
}

VB.Net

Protected Sub OnSave(ByVal sender As Object, ByVal e As EventArgs)
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(2) {
        New DataColumn("PERSONAL_EMAILID"), New DataColumn("ENAME"), New DataColumn("OFFICIAL_EMAILID")})
    dt.Rows.Add("test1@gmail.com", "Test 1", "test2@gmail.com")
    dt.Rows.Add("test3@gmail.com", "Test 2", "test4@gmail.com")

    Dim fs As Stream = fileUploader.PostedFile.InputStream
    Dim br As BinaryReader = New BinaryReader(fs)
    Dim bytes As Byte() = br.ReadBytes(CType(fs.Length, Int32))
    Dim fileName As String = Path.GetFileName(fileUploader.PostedFile.FileName)

    Parallel.ForEach(dt.AsEnumerable(), Function(row)
        SendEmail(row("PERSONAL_EMAILID").ToString(), txtsubject.Text, String.Format("{0}", row("ENAME")), fileName, bytes)
        SendEmail(row("OFFICIAL_EMAILID").ToString(), txtsubject.Text, String.Format("{0}", row("ENAME")), fileName, bytes)
    End Function)
End Sub

Private Sub SendEmail(ByVal recipient As String, ByVal subject As String, ByVal body As String, ByVal fileName As String, ByVal bytes As Byte())
    Dim from As String = txtemailfrom.Text
    Using mail As MailMessage = New MailMessage(from, recipient)
        mail.Subject = subject
        mail.Body = body
        If bytes.Length > 0 Then
            mail.Attachments.Add(New Attachment(New MemoryStream(bytes), fileName))
        End If
        mail.IsBodyHtml = False
        Dim smtp As SmtpClient = New SmtpClient()
        smtp.Host = "smtp.gmail.com"
        smtp.EnableSsl = True
        Dim networkCredential As NetworkCredential = New NetworkCredential(from, "password")
        smtp.UseDefaultCredentials = True
        smtp.Credentials = networkCredential
        smtp.Port = 25
        smtp.Send(mail)
        ScriptManager.RegisterStartupScript(Me, Me.GetType(), "alert", "alert('Message has been sent successfully.');window.location ='SendBulkMail.aspx';", True)
    End Using
End Sub