static string ReplaceEmbeddedImages(string htmlBody, AttachmentCollection attachments)
{
var srcPattern =
"(?<=<img.+?src=[\"'])" +
"(.+?)" +
"(?=[\"'].*?>)";
// Iterate through "src" attributes from HTML images in reverse order.
foreach (var match in Regex.Matches(htmlBody, srcPattern, RegexOptions.IgnoreCase).Cast <Match>().Reverse())
{
var imageId = match.Value.Replace("cid:", "");
Attachment attachment = attachments.FirstOrDefault(a => a.ContentId == imageId);
if (attachment != null)
{
// Create inlined image data. E.g. "data:image/png;base64,AABBCC..."
ContentEntity entity = attachment.MimeEntity;
var embeddedImage = entity.Charset.GetString(entity.Content);
var embeddedSrc = $"data:{entity.ContentType};{entity.TransferEncoding},{embeddedImage}";
// Replace "src" attribute with inlined image.
htmlBody = $"{htmlBody.Substring(0, match.Index)}{embeddedSrc}{htmlBody.Substring(match.Index + match.Length)}";
}
}
return(htmlBody);
}