How to embed multiple images in email body using .NET

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I\'m writing a program that sends emails to users with multiple images (charts) embedded in the Email message body (HTML).

When I tried the sample located here..whic

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时光说笑

2020-11-29 06:36
if you have the images online, meaning sending from a hosted site, i suggest you just reference those images simply by putting their url in the src.
```

<IMG SRC="http://www.ietf.cnri.reston.va.us/images/ietflogo.gif" ALT="IETF logo" />
```
most of the newsletters use this method, and i believe it's lighter and can consume less resources than embedding itself.

hope this helps
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长情又很酷

2020-11-29 06:42

The other way to embed images in E-mail when using System.Net.Mail is

Attach image from local drive to email and assign a contentID to it and later use this contentID in the image URL.

This can be done by:

var contentID = "Image";
var inlineLogo = new Attachment(@"C:\Desktop\Image.jpg");
inlineLogo.ContentId = contentID;
inlineLogo.ContentDisposition.Inline = true;
inlineLogo.ContentDisposition.DispositionType = DispositionTypeNames.Inline;

msg.IsBodyHtml = true;
msg.Attachments.Add(inlineLogo);
msg.Body = "<htm><body> <img src=\"cid:" + contentID + "\"> </body></html>";

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后悔当初

2020-11-29 06:43

My alternatie:

First of all, a little extension:

public static class RegexExtensions
{
    public static string GetPattern(this IEnumerable<string> valuesToSearch)
    {
        return string.Format("({0})", string.Join("|", valuesToSearch));
    }
}

then get image names from folder:

    private string[] GetFullNamesOfImages()
    {
        string images = Path.Combine(_directoryName, "Images");
        if (!Directory.Exists(images))
            return new string[0];
        return Directory.GetFiles(images);
    }

then replacing image names by cid:

    private string InsertImages(string body)
    {
        var images = GetFullNamesOfImages().Select(Path.GetFileName).ToArray();
        return Regex.Replace(body, "(Images/)?" + images.GetPattern(), "cid:$2", RegexOptions.IgnoreCase | RegexOptions.Compiled);
    }

where body - is HTML body, and for example, <img src="Images/logo_shadow.png" alt="" style="width: 100%;" /> will be replaced by <img src="cid:logo_shadow.png" alt="" style="width: 100%;" />

then last action: adding images itselfs to mail:

    private MailMessage CreateMail(SmtpClient smtp, string toAddress, string body)
    {
        var images = GetFullNamesOfImages();

        string decodedBody = WebUtility.HtmlDecode(body);
        var text = AlternateView.CreateAlternateViewFromString(decodedBody, null, MediaTypeNames.Text.Plain);
        var html = AlternateView.CreateAlternateViewFromString(body, null, MediaTypeNames.Text.Html);
        foreach (var image in images)
        {
            html.LinkedResources.Add(new LinkedResource(image, new ContentType("image/png"))
                                     {
                                         ContentId = Path.GetFileName(image)
                                     });
        }


        var credentials = (NetworkCredential) smtp.Credentials;

        var message = new MailMessage(new MailAddress(credentials.UserName), new MailAddress(toAddress))
                      {
                          Subject = "Some subj",
                          Body = decodedBody
                      };
        message.AlternateViews.Add(text);
        message.AlternateViews.Add(html);
        return message;
    }

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盖世英雄少女心

2020-11-29 06:48

So, I think figured out what the actual problem is Its in this line

// Alternate view for embedded images
    AlternateView avText = AlternateView.CreateAlternateViewFromString(metric.Name, null, MediaTypeNames.Text.Html);
    AlternateView avImages = AlternateView.CreateAlternateViewFromString(htmlBody, null, MediaTypeNames.Text.Html);

As you can see, both my views are specified as Text.Html, so the the 1st one is overriding the next one and so I only see text and images are sent as attachments

I made the following change and it worked as expected

AlternateView avText = AlternateView.CreateAlternateViewFromString(metric.Name, null, **MediaTypeNames.Text.Plain**);
AlternateView avImages = AlternateView.CreateAlternateViewFromString(htmlBody, null, MediaTypeNames.Text.Html);

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不思量自难忘°

2020-11-29 06:53

First, you could try to use absolute URIs to embedded images. Here is example from RFC-2557:

  From: foo1@bar.net
  To: foo2@bar.net
  Subject: A simple example
  Mime-Version: 1.0
  Content-Type: multipart/related; boundary="boundary-example";
          type="text/html"; start="<foo3@foo1@bar.net>"

  --boundary-example
  Content-Type: text/html;charset="US-ASCII"
  Content-ID: <foo3@foo1@bar.net>

  ... text of the HTML document, which might contain a URI
  referencing a resource in another body part, for example
  through a statement such as:
  <IMG SRC="http://www.ietf.cnri.reston.va.us/images/ietflogo.gif" ALT="IETF logo">

  --boundary-example
  Content-Location:
     http://www.ietf.cnri.reston.va.us/images/ietflogo.gif
  Content-Type: IMAGE/GIF
  Content-Transfer-Encoding: BASE64

  R0lGODlhGAGgAPEAAP/////ZRaCgoAAAACH+PUNvcHlyaWdodCAoQykgMTk5
  NSBJRVRGLiBVbmF1dGhvcml6ZWQgZHVwbGljYXRpb24gcHJvaGliaXRlZC4A
  etc...

  --boundary-example--

You just need to assign LinkedResource.ContentLink property instead of ContentId.

Second, you could embed images directly to your html with the "data" URL scheme.

    <IMG
    SRC="data:image/gif;base64,R0lGODdhMAAwAPAAAAAAAP///ywAAAAAMAAw
    AAAC8IyPqcvt3wCcDkiLc7C0qwyGHhSWpjQu5yqmCYsapyuvUUlvONmOZtfzgFz
    ByTB10QgxOR0TqBQejhRNzOfkVJ+5YiUqrXF5Y5lKh/DeuNcP5yLWGsEbtLiOSp
    a/TPg7JpJHxyendzWTBfX0cxOnKPjgBzi4diinWGdkF8kjdfnycQZXZeYGejmJl
    ZeGl9i2icVqaNVailT6F5iJ90m6mvuTS4OK05M0vDk0Q4XUtwvKOzrcd3iq9uis
    F81M1OIcR7lEewwcLp7tuNNkM3uNna3F2JQFo97Vriy/Xl4/f1cf5VWzXyym7PH
    hhx4dbgYKAAA7"
    ALT="Larry">

BTW, your html markup is not well-formed. You may also be interested in “foreach” vs “ForEach”

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南笙

2020-11-29 06:53

        AlternateView avHtml = AlternateView.CreateAlternateViewFromString(body, null, MediaTypeNames.Text.Html);
        LinkedResource inline = new LinkedResource(System.Web.HttpContext.Current.Server.MapPath("~/Images/e1.jpg"), MediaTypeNames.Image.Jpeg);
        inline.ContentId = "1";
        inline.TransferEncoding = System.Net.Mime.TransferEncoding.Base64;
        avHtml.LinkedResources.Add(inline);

        LinkedResource inline1 = new LinkedResource(System.Web.HttpContext.Current.Server.MapPath("~/CImages/2.jpg"), MediaTypeNames.Image.Jpeg);
        inline1.ContentId = "2";
        inline1.TransferEncoding = System.Net.Mime.TransferEncoding.Base64;
        avHtml.LinkedResources.Add(inline1);

        LinkedResource inline2 = new LinkedResource(System.Web.HttpContext.Current.Server.MapPath("~/Images/3.jpg"), MediaTypeNames.Image.Jpeg);
        inline2.ContentId = "3";
        inline2.TransferEncoding = System.Net.Mime.TransferEncoding.Base64;
        avHtml.LinkedResources.Add(inline2);

        LinkedResource inline3 = new LinkedResource(System.Web.HttpContext.Current.Server.MapPath("~/Content/Images/4.jpg"), MediaTypeNames.Image.Jpeg);
        inline3.ContentId = "4";
        inline3.TransferEncoding = System.Net.Mime.TransferEncoding.Base64;
        avHtml.LinkedResources.Add(inline3);

        MailMessage mail = new MailMessage();
        mail.AlternateViews.Add(avHtml);

HTML:

       <img src="cid:1" alt="" />
       <img src="cid:2" alt="" />
       <img src="cid:3" alt="" /`
       <img src="cid:4" alt="" />

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