In this article I will explain with an example, how to send email with attachment from Folder (Directory) in ASP.Net Core (.Net Core).
Note: For beginners in ASP.Net Core (.Net Core 7), please refer my article ASP.Net Core 7: Hello World Tutorial with Sample Program example.
 
 

Attachment File location

The File which will be used as Attachment is located inside the Folder (Directory) named Files inside the wwwroot Folder(Directory).
ASP.Net Core: Send Email with attachment from Folder (Directory)
 
 

Mail Server Settings in AppSettings.json file

The following Mail Server settings need to be saved in the AppSettings.json file. 
{
    "Smtp": {
        "Server": "smtp.gmail.com",
        "Port": 587,
        "EnableSsl": true,
        "DefaultCredentials": false
    }
}
 
 

Sending Email using Gmail SMTP

MailMessage class properties

Following are the required properties of the MailMessage class.
From – Sender’s email address.
To – Recipient(s) Email Address.
CC – Carbon Copies. (If any)
BCC – Blind Carbon Copies. (If any)
Subject – Subject of the Email.
Body – Body of the Email.
IsBodyHtml – Specify whether body contains text or HTML mark up.
Attachments – Attachments. (If any)
ReplyTo – ReplyTo Email address.
 

SMTP class properties

Following are the properties of the SMTP class.
Host – SMTP Server URL. (Gmail: smtp.gmail.com)
EnableSsl – Specify whether your host accepts SSL Connections. (Gmail: True)
UseDefaultCredentials – Set to True in order to allow authentication based on the Credentials of the Account used to send emails.
Credentials – Valid login credentials for the SMTP server. (Gmail: email address and password)
Port – Port Number of the SMTP server. (Gmail: 587)
 
 

Model

The Model class consists of following properties.
public class EmailModel
{
    public string To { get; set; }
    public string Subject { get; set; }
    public string Body { get; set; }
    public string Email { get; set; }
    public string Password { get; set; }
}
 
 

Namespaces

You will need to import the following namespaces.
using System.Net;
using System.Net.Mail;
 
 

Controller

The Controller consists of following Action methods.

Action method for handling GET operation

Inside this Action method, simply the View is returned.
 

Action method for handling POST operation

Inside this Action method, the posted values are captured through the EmailModel class object. All the fetched values are set into an object of the MailMessage class except Attachment.

Setting Body of Email

The Body of the email is Text (Non HTML) hence the IsBodyHtml property of MailMessage class is set to FALSE.

Attaching File

The full path where the file for attachment is located (explained earlier) is fetched using IWebHostEnvironment interface.
Note: The IWebHostEnvironment interface is injected using Dependency Injection inside the Controller, for more details please refer Using IWebHostEnvironment in ASP.Net Core.
        For more details on how to access Static Files in Core, please refer my article Static Files (Images, CSS and JS files) in ASP.Net Core.
 
The BYTE array of that file is fetched using ReadAllBytes method of the File class and added as Attachment to the MailMessage class object.

Sending Email

Then, an object of the SmtpClient class is created and the values of Host, Port, EnableSsl and UseDefaultCredentials are fetched from the SMTP section of the AppSettings.json file and set to the respective properties of SmtpClient class along with the Credentials.
Finally, the Send method is executed which sends the Email and a success message is set to a ViewBag object.
public class HomeController : Controller
{
    public IConfiguration Configuration { get; set; }
    private IWebHostEnvironment Environment;
 
    public HomeController(IConfiguration _configuration, IWebHostEnvironment _environment)
    {
        this.Configuration = _configuration;
        this.Environment = _environment;
    }
 
    public IActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public IActionResult Index(EmailModel model)
    {
        //Read SMTP section from AppSettings.json.
        string host = this.Configuration.GetValue<string>("Smtp:Server");
        int port = this.Configuration.GetValue<int>("Smtp:Port");
        bool enableSsl = this.Configuration.GetValue<bool>("Smtp:EnableSsl");
        bool defaultCredentials = this.Configuration.GetValue<bool>("Smtp:DefaultCredentials");
 
        using (MailMessage mm = new MailMessage(model.Email, model.To))
        {
            mm.Subject = model.Subject;
            mm.Body = model.Body;
            mm.IsBodyHtml = false;`
            string filePath = Path.Combine(this.Environment.WebRootPath,"Files/Test.pdf");
            if (System.IO.File.Exists(filePath))
            {
                //Reading file name.
                string fileName = Path.GetFileName(filePath);
                //Reading the file into byte array.
                byte[] bytes = System.IO.File.ReadAllBytes(filePath);
                //Attaching file from Folder/Directory.
                mm.Attachments.Add(new Attachment(new MemoryStream(bytes), fileName));
            }
            using (SmtpClient smtp = new SmtpClient())
            {
                smtp.Host = host;
                smtp.Port = port;
                smtp.EnableSsl = enableSsl;
                smtp.UseDefaultCredentials = defaultCredentials;
                NetworkCredential networkCred = new NetworkCredential(model.Email, model.Password);
                smtp.Credentials = networkCred;
                smtp.Send(mm);
                ViewBag.Message = "Email sent.";
            }
        }
        return View();
    }
}
 
 

View

HTML Markup

Inside the View, the EmailModel class is declared as model for the View and ASP.Net TagHelpers in inherited.
The View consists of an HTML Form which has been created using the following TagHelpers attributes.
asp-action – Name of the Action. In this case the name is Index.
asp-controller – Name of the Controller. In this case the name is Home.
method – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
The HTML Form has been specified with enctype=“multipart/form-data” attribute as it is necessary for File Upload operation.
The Form consists of HTML TextBox, TextArea, FileUpload element and a Submit Button.
When the Submit Button is clicked, the Form gets submitted and the Model object is sent to the Controller. 
 

Submitting the Form

Finally, the ViewBag object is checked for NULL and if it is not NULL then the value of the object is displayed using JavaScript Alert Message Box.
@model Send_Email_MVC_Core.Models.EmailModel
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <form method="post" asp-controller="Home" asp-action="Index" enctype="multipart/form-data">
        <table>
            <tr>
                <td style="width: 80px">To:</td>
                <td><input type="text" asp-for="To" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td>Subject:</td>
                <td><input type="text" asp-for="Subject" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td valign="top">Body:</td>
                <td><textarea cols="20" rows="3" asp-for="Body"></textarea></td>
            </tr>
            <tr><td>&nbsp;</td></tr>           
            <tr>
                <td>File Attachment:</td>
                <td><input type="file" asp-for="Attachment" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td>Gmail Email:</td>
                <td><input type="text" asp-for="Email" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td>Gmail Password:</td>
                <td><input type="password" asp-for="Password" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td></td>
                <td><input type="submit" value="Send" /></td>
            </tr>
        </table>
    </form>
    @if (ViewBag.Message != null)
    {
        <script type="text/javascript">
            window.onload = function () {
                alert("@ViewBag.Message");
            };
        </script>
    }
</body>
</html>
 
 

Possible Error

The following error occurs when you try to send email using Gmail credentials in your application.
The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at
 

Solution

GMAIL Error: The SMTP server requires a secure connection or the client was not authenticated.
 
 

Screenshot

Email Form

ASP.Net Core: Send Email with attachment from Folder (Directory)
 

Received Email

ASP.Net Core: Send Email with attachment from Folder (Directory)
 
 

Downloads

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