Introduction

This article explains how to send an email with attachments using SmtpClient.SendAsync. My previous article explained sending Asynchronous Emails in ASP.NET 4.5 I will now explain how to implement send asynchronous mail with an attachment in ASP.NET 4.5.

Creating an Asynchronous Page

Create a new project using "File" -> "New" -> "Project..." then select web "ASP .Net Web Forms Application". Name it " SendMailAsyncAttachment ".

Send Asynchronous Mail1

Next, create the code-behind as follows: The first step to building an asynchronous page is setting the Async attribute in the Page directive to true, as shown here:



<%@ Page Language="C#" Async="true" %>

Now, in the code behind file SendMailAttach.aspx use the following code.

SendMailAttach.aspx

  1. <%@ Page Title="Sendmailasync with attachment" Async="true" Language="C#"
  2. MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="SendMailAttach.aspx.cs"
  3. Inherits="SendMailAsyncAttachment.SendMailAttach" %
  4. <asp:Content ID="Content1" ContentPlaceHolderID="titleContent" runat="server">Sendmailasync with
  5. attachment
  6. </asp:Content>
  7. <asp:Content ID="Content2" ContentPlaceHolderID="head" runat="server">
  8. <script type="text/javascript">
  9. function validationCheck() {
  10. var summary = "";
  11. summary += isvalidName();
  12. summary += isvalidEmail();
  13. summary += isvalidSubject();
  14. summary += isvalidMessage();
  15. if (summary != "") {
  16. alert(summary);
  17. return false;
  18. }
  19. else {
  20. return true;
  21. }
  22. }
  23. function isvalidName() {
  24. var id;
  25. var temp = document.getElementById("<%=txtName.ClientID %>");
  26. id = temp.value;
  27. if (id == "") {
  28. return ("Please enter Name" + "\n");
  29. }
  30. else {
  31. return "";
  32. }
  33. }
  34. function isvalidEmail() {
  35. var id;
  36. var temp = document.getElementById("<%=txtEmail.ClientID %>");
  37. id = temp.value;
  38. var re = /\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*/;
  39. if (id == "") {
  40. return ("Please Enter Email" + "\n");
  41. }
  42. else if (re.test(id)) {
  43. return "";
  44. }
  46. else {
  47. return ("Email should be in the form [email protected]" + "\n");
  48. }
  49. }
  50. function isvalidSubject() {
  51. var id;
  52. var temp = document.getElementById("<%=txtSubject.ClientID %>");
  53. id = temp.value;
  54. if (id == "") {
  55. return ("Please enter Subject" + "\n");
  56. }
  57. else {
  58. return "";
  59. }
  60. }
  61. function isvalidMessage() {
  62. var id;
  63. var temp = document.getElementById("<%=txtMessage.ClientID %>");
  64. id = temp.value;
  65. if (id == "") {
  66. return ("Please enter Message" + "\n");
  67. }
  68. else {
  69. return "";
  70. }
  71. }
  73. </script>
  74. </asp:Content>
  75. <asp:Content ID="Content3" ContentPlaceHolderID="MainContent" runat="server">
  76. <table style="width: 100%;">
  77. <tr>
  78. <td>Name:</td>
  79. <td>
  80. <asp:TextBox ID="txtName" runat="server" CssClass="txt"></asp:TextBox></td>
  81. <td> </td>
  82. </tr>
  83. <tr>
  84. <td>Email ID:</td>
  85. <td>
  86. <asp:TextBox ID="txtEmail" runat="server" CssClass="txt"></asp:TextBox></td>
  87. <td> </td>
  88. </tr>
  89. <tr>
  90. <td>Subject:</td>
  91. <td>
  92. <asp:TextBox ID="txtSubject" runat="server" CssClass="txt"></asp:TextBox></td>
  93. <td> </td>
  94. </tr>
  95. <tr>
  96. <td>Attach a file:</td>
  97. <td>
  98. <asp:FileUpload ID="FileUpload1" runat="server" AllowMultiple="true" />
  99. </td>
  100. <td></td>
  101. </tr>
  102. <tr>
  103. <td>Message:</td>
  104. <td>
  105. <asp:TextBox ID="txtMessage" runat="server" Height="100px" Width="200px"
  106. CssClass="textarea" TextMode="MultiLine"></asp:TextBox>
  107. </td>
  108. <td> </td>
  109. </tr>
  110. <tr>
  111. <td></td>
  112. <td>
  113. <asp:Button ID="btnSendMail" runat="server" Text="Send Mail" CssClass="button"
  114. OnClick="btnSendMail_Click" /></td>
  115. </tr>
  116. </table>
  117. </asp:Content>
Create a SmtpClient.SendCompleted Event and SmtpClient.SendAsyncCancel Method and attachment

Now, in the code behind file “SendMailAttach.aspx.cs “ use the following code.

SendMailAttach.aspx.cs

  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Web;
  5. using System.Web.UI;
  6. using System.Web.UI.WebControls;
  7. using System.IO;
  8. using System.Net;
  9. using System.Net.Mail;
  10. using System.Net.Mime;
  11. using System.Threading;
  12. using System.ComponentModel;
  13. using System.Text;
  14. using System.Web.Util;
  16. namespace SendMailAsyncAttachment
  17. {
  18. public partial class SendMailAttach : System.Web.UI.Page
  19. {
  20. protected void Page_Load(object sender, EventArgs e)
  21. {
  22. Try
  23. {
  24. if (!Page.IsPostBack)
  25. {
  26. btnSendMail.Attributes.Add("onclick", "javascript:return validationCheck()");
  27. }
  28. }
  29. catch (Exception ex)
  30. {
  31. ShowMessage(ex.Message);
  32. }
  33. }
  34. #region show message
  35. /// <summary>
  36. /// This function is used for show message.
  37. /// </summary>
  38. /// <param name="msg"></param>
  39. void ShowMessage(string msg)
  40. {
  41. ClientScript.RegisterStartupScript(Page.GetType(), "validation", "<script
  42. language='javascript'>alert('" + msg + "');</script>");
  43. }
  44. #endregion
  45. #region SendAsyncCancel
  46. /// <summary>
  47. /// this code used to SmtpClient.SendAsyncCancel Method
  48. /// </summary>
  49. // static bool mailSent = false;
  50. void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
  51. {
  52. if (e.Cancelled)
  53. {
  54. ShowMessage("Send canceled.");
  55. }
  56. if (e.Error != null)
  57. {
  58. ShowMessage(e.Error.ToString());
  59. }
  60. else
  61. {
  62. ShowMessage("Email sent successfully");
  63. }
  64. }
  65. #endregion
  66. #region SendMailAsync
  67. /// <summary>
  68. /// this code used to SmtpClient.SendCompleted Event and attaching the file
  69. /// </summary>
  70. /// <param name="sender"></param>
  71. /// <param name="e"></param>
  72. protected void btnSendMail_Click(object sender, EventArgs e)
  73. {
  74. Try
  75. {
  76. MailMessage message = new MailMessage();
  77. message.To.Add(txtEmail.Text.Trim());
  78. message.From = new MailAddress("[email protected]","Sendmailasync Test");
  79. message.Subject = txtSubject.Text.Trim();
  80. message.Body = txtMessage.Text.Trim();
  81. message.IsBodyHtml = true;
  82. if (FileUpload1.HasFile)
  83. {
  84. message.Attachments.Add(new Attachment(FileUpload1.PostedFile.InputStream,
  85. FileUpload1.FileName));
  86. }
  87. SmtpClient smtp = new SmtpClient();
  88. smtp.Host = "smtp.gmail.com";
  89. smtp.Credentials = new System.Net.NetworkCredential("[email protected]", "YouPassword");
  90. smtp.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);
  91. smtp.EnableSsl = true;
  92. smtp.SendMailAsync(message);
  93. }
  94. catch (Exception ex)
  95. {
  96. ShowMessage(ex.Message);
  97. }
  98. clear();
  99. }
  100. #endregion
  101. #region
  102. /// <summary>
  103. /// This Function is used TextBox Empty.
  104. /// </summary>
  105. void clear()
  106. {
  107. txtName.Text = string.Empty; txtEmail.Text = string.Empty; txtSubject.Text = string.Empty;
  108. txtMessage.Text = string.Empty;
  109. txtName.Focus();
  110. }
  111. #endregion
  112. }
  113. }

Now run the page, it will look like this:

Send Asynchronous Mail3

Now, show in the Message box “Email sent successfully”.

Send Asynchronous Mail4

Now, see the following screen: SendMailAsync with Attachment.

Send Asynchronous Mail5

I hope this article is useful. If you have any other questions then please provide your comments in the following.