电子邮件附件中的 c# Base64

Question

我知道我陷入了一个愚蠢的问题......现在我带着希望来到这里，希望你能帮助我。简单的情况：我需要从数据库发送带有附件的电子邮件。我自己完成了，但是......我不知道为什么，但是电子邮件中发送的附件不正确。珍贵的附件内容代码，是我从数据库中获得的。

我的代码：

static void IncomeMessage()
{
    SqlConnection conn = new SqlConnection("Data Source=xxx;Initial Catalog=xxx;User ID=xxx;Password=xxx");
    SqlCommand cmd = new SqlCommand("Here is my SQL SELECT", conn);
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    da.Fill(dt);

    foreach (DataRow dr in dt.Rows)
    {
        try
        {
            var AID = dr["ID"].ToString();
            var Ids = dr["MessageID"].ToString();
            var SuperOrganizationTitle = dr["SuperOrganizationTitle"].ToString();
            var Date = dr["Date"].ToString();
            var Title = dr["Title"].ToString();
            var Description = dr["Description"].ToString();
            var DBFile = dr["File"].ToString();
            var Filename = dr["FileName"].ToString();

            MailMessage oMail = new MailMessage("test@test.com", "guntisvindels@gmail.com", "New message with theme: " + Title, "Message Income: " + Date + " From " + SuperOrganizationTitle + ". Message Content: " + Description);

            DBFile = GetBase64(DBFile);

            var bytes = Encoding.ASCII.GetBytes(DBFile);
            MemoryStream strm = new MemoryStream(bytes);
            Attachment data = new Attachment(strm, Filename);
            ContentDisposition disposition = data.ContentDisposition;
            data.ContentId = Filename;
            data.ContentDisposition.Inline = true;
            oMail.Attachments.Add(data);

            SmtpClient oSmtp = new SmtpClient();
            SmtpClient oServer = new SmtpClient("test.test.com");

            oServer.Send(oMail);
        }
        catch (Exception ex)
        {
            //TraceAdd("Error=" + ex.Message.ToString());
        }
    }
}

为了从数据库文件字段中删除不必要的数据（标签），我使用此代码

public static string GetBase64(string str)
{
    var index1 = str.IndexOf("<content>");
    index1 = index1 + "<content>".Length;
    var index2 = str.IndexOf("</content>");
    var kek = Slice(str, index1, index2);
    return kek;
}

public static string Slice(string source, int start, int end)
{
    if (end < 0)
    {
        end = source.Length + end;
    }
    int len = end - start;
    return source.Substring(start, len);
}

当启动我的代码时，我可以向我发送电子邮件，我会收到它。但消息内容附件带有我的数据库文件字段中的 Base64 代码。这是一个问题 - 我哪里出错了，如何才能收到已写入数据库的带有正确附件的电子邮件。感谢您的关注

PS数据库中的附件写入正确，因为K2集成平台可以正确显示

这是数据库在文件列（DBFile）中包含的示例

<file><name>zinojums.html</name><content>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</content></file>

Answer 1

现在，您用于从字符串创建二进制数据的方法没有考虑字符串是专门进行 Base64 编码的事实。

你需要更换

var bytes = Encoding.ASCII.GetBytes(DBFile);

和

var bytes = Convert.FromBase64String(DBFile);