如何在AlternateView上设置编码

我正在通过创建邮件正文

using (var streamWriter = new StreamWriter(fooFileName, false, Encoding.UTF8))
{
    streamWriter.Write(fooMessage);
}

现在我用这个文件

var mailMessage = new System.Net.Mail.MailMessage
{
    From = fooSender,
    To =
    {
        fooRecipient
    },
    Subject = fooSubject,
    SubjectEncoding = Encoding.UTF8,
    BodyEncoding = Encoding.UTF8
};
// fooMediaType can be
// - System.Net.Mime.MediaTypeNames.Text.Html
// - System.Net.Mime.MediaTypeNames.Text.Plain
var alternateView = new System.Net.Mail.AlternateView(fooFileName, fooMediaType);
mailMessage.AlternateViews.Add(alternateView);

如果我使用的是非umlauts,一切正常,但只要我在我的 alternateView ,它们会破碎。

那么,如何在AlternateView上设置某种编码,以确保一切正常工作?