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首页 > 解决方案 > 使用 MimeKit 从数据库读取时，电子邮件的富字符被错误翻译

asp.net - 使用 MimeKit 从数据库读取时，电子邮件的富字符被错误翻译

问题描述

我有一个用 VB.Net 编写的 Windows 服务，它将电子邮件下载到 MimeMessage 对象中，删除它们的附件，然后将电子邮件的剩余部分写入 SQL Server 数据库。一个单独的 ASP.Net 应用程序（使用 VB.Net）将电子邮件读回 MimeMessage 对象，并根据请求将其返回给用户。

在此过程中发生了一些事情，导致输出中出现奇怪的字符。

这个问题（使用 MimeKit/MailKit 进行内容编码）似乎很有希望，但是将字符编码从 ASCII 更改为 UTF8 等并没有解决它。

以下是将电子邮件保存到数据库的代码：

Sub ImportEmail(exConnectionString As String)
    Dim oClient As New Pop3Client()
    ' … email connection code removed …
    Dim message = oClient.GetMessage(0)
    Dim strippedMessage As MimeMessage = message
    ' … code to remove attachments removed …
    Dim mem As New MemoryStream
    strippedMessage.WriteTo(mem)
    Dim bytes = mem.ToArray
    Dim con As New SqlConnection(exConnectionString)
    con.Open()
    Dim com As New SqlCommand("INSERT INTO Emails (Body) VALUES (@RawDocument)", con)
    com.CommandType = CommandType.Text
    com.Parameters.AddWithValue("@RawDocument", bytes)
    com.ExecuteNonQuery()
    con.Close()
End Sub

这是用于将其读回给用户的 ASP.Net 代码：


Private Sub OutputEmail(exConnectionString As String)
    Dim BlobString As String = ""
    Dim Sql As String = "SELECT Body FROM Emails WHERE Id = @id"    
    Dim com As New SqlClient.SqlCommand(Sql)
    com.CommandType = CommandType.Text
    com.Parameters.AddWithValue("@id", ViewState("email_id")) 

    Dim con As New SqlConnection(exConnectionString)
    con.Open()
    com.Connection = con
    Dim da As New SqlClient.SqlDataAdapter(com)
    Dim dt As New DataTable()
    da.Fill(dt)
    con.Close()

    If dt.Rows.Count > 0 Then
        Dim Row = dt.Rows(0)
        BlobString = Row(0).ToString()

        Dim MemStream As MemoryStream = GetMemoryStreamFromASCIIEncodedString(BlobString)
        Dim message As MimeMessage = MimeMessage.Load(MemStream)

        BodyBuilder.HtmlBody = message.HtmlBody
        BodyBuilder.TextBody = message.TextBody
        message.Body = BodyBuilder.ToMessageBody()

        Response.ContentType = "message/rfc822"
        Response.AddHeader("Content-Disposition", "attachment;filename=""" & Left(message.Subject, 35) & ".eml""")
        Response.Write(message)
        Response.End()
    End If
End Sub

Private Function GetMemoryStreamFromASCIIEncodedString(ByVal BlobString As String) As MemoryStream
    Dim BlobStream As Byte() = Encoding.ASCII.GetBytes(BlobString) ' **
    Dim MemStream As MemoryStream = New MemoryStream()
    MemStream.Write(BlobStream, 0, BlobStream.Length)
    MemStream.Position = 0
    Return MemStream
End Function

例如，假设以下文本出现在原始电子邮件中：

“So long and thanks for all the fish” (fancy quotes)

回读时，显示如下：

†So long and thanks for all the fishâ€

其他字符替换如下：

– （长破折号）变为 ¢€“</p>

•（子弹）变成•</p>

标签： asp.net.netvb.netmimekit

解决方案

问题在于以下代码段：

If dt.Rows.Count > 0 Then
    Dim Row = dt.Rows(0)
    BlobString = Row(0).ToString() ' <-- the ToString() is the problem

    Dim MemStream As MemoryStream = GetMemoryStreamFromASCIIEncodedString(BlobString)
    Dim message As MimeMessage = MimeMessage.Load(MemStream)

要修复数据损坏，您需要做的是：

If dt.Rows.Count > 0 Then
    Dim Row = dt.Rows(0)
    Dim BlobString as Byte() = Row(0)

    Dim MemStream As MemoryStream = new MemoryStream (BlobString, False)
    Dim message As MimeMessage = MimeMessage.Load(MemStream)

你也可以摆脱你的GetMemoryStreamFromASCIIEncodedString功能。

（注意：我不知道 VB.NET，所以我只是猜测语法，但应该非常接近正确）

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