如何通过MemoryStream在MailKit邮件正文中嵌入图片？

你已经实现了从资源文件读取图片并转成MemoryStream的逻辑，但没用到它。下面是修改后的代码，直接用MemoryStream嵌入图片，去掉硬编码路径：

修改后的核心代码 #

using MailKit.Net.Smtp;
using MailKit;
using System.Drawing.Imaging;

public static List<MessageSet> MessageList = new List<MessageSet>();
public static void SendErrorNotification(MONMessage message)  
{
    var email = new MimeMessage();

    try
    {
        var supportImage = GetImageByName("support_image.jpg");
        // 直接将Bitmap保存到MemoryStream，比转byte[]更简洁
        MemoryStream imageMemoryStream = new MemoryStream();
        supportImage.Save(imageMemoryStream, ImageFormat.Jpeg);
        imageMemoryStream.Position = 0; // 重置流位置，确保能被读取

        var validateMessage = MessageList.Where(m => m.MessageTime == message.MessageTime && m.MessageSetVal == message.MessageSet && m.MessageStatus == message.Status);

        if (validateMessage.Count() == 0)
        {
            email.From.Add(new MailboxAddress("Monitor", "m.long@myself.com"));
            email.To.Add(new MailboxAddress("Lancair", "m.long@myself.com"));
            email.Subject = "Environment Error Found - Please Review";

            var Name = string.IsNullOrEmpty(message.Name) ? "N/A" : message.Name;

            var emailText = "<br><br>" + "The following error has occurred within the Data Environment" + "<br>"
            + "Time: " + message.MessageTime + "<br>"
            + " Database: " + message.DBName + "<br>"
            + " Name: " + Name + "<br>"
            + " Event Id: " + message.EventID + "<br>"
            + " Message: " + message.Text + "</b>";

            BodyBuilder _body = new BodyBuilder
            {
                HtmlBody = emailText, // 直接用文本，不用先转TextPart
            };

            // 使用MemoryStream添加LinkedResource
            var image = _body.LinkedResources.Add("support_image.jpg", imageMemoryStream);
            image.ContentId = MimeUtils.GenerateMessageId();

            // 拼接HTML，嵌入图片
            _body.HtmlBody = string.Format("<p>Hello Support</p><br><img src=\"cid:{0}\">", image.ContentId) + _body.HtmlBody;

            email.Body = _body.ToMessageBody();

            // 添加到已发送列表
            MessageList.Add(new MessageSet { MessageTime = message.MessageTime, MessageSetVal = message.MessageSet, MessageStatus = message.Status });

            using (var smtp = new SmtpClient())
            {
                smtp.Connect("mymail.home.com", 0, false);
                smtp.Send(email);
                smtp.Disconnect(true);
            }
        }
    }
    catch (Exception ex) 
    { 
        Debug.WriteLine(ex.Message); 
    }                        
}

public static Bitmap GetImageByName(string imageName)
{
    System.Reflection.Assembly asm = System.Reflection.Assembly.GetExecutingAssembly();
    string resourceName = asm.GetName().Name + ".Properties.Resources";
    var rm = new System.Resources.ResourceManager(resourceName, asm);
    return (Bitmap)rm.GetObject(imageName);
}

关键修改点 #

• 简化Bitmap转流逻辑：直接用Bitmap.Save()将图片写入MemoryStream，比手动处理BitmapData更可靠，自动适配图片格式编码。
• 重置流位置：写入MemoryStream后必须将Position设为0，否则MailKit读取流时会从末尾开始，导致图片内容为空。
• 使用Stream重载方法：调用LinkedResources.Add(string fileName, Stream stream)，fileName用于自动识别MIME类型（比如.jpg对应image/jpeg），也可以手动指定ContentType：

  var image = _body.LinkedResources.Add(imageMemoryStream);
  image.ContentType = new ContentType("image", "jpeg");
  image.ContentId = MimeUtils.GenerateMessageId();
  

• 精简HTML构建：不需要先创建TextPart再转字符串，直接将HTML文本赋值给BodyBuilder的HtmlBody。

内容的提问来源于stack exchange，提问作者user2284452