C#/ BinaryWriter:输出流中出现的怪异角色

Question

我很难搞清楚导致输出流中出现奇怪字符的原因...完整代码@pastebin

提琴手输出

在我的边界之前注意" s"," X"," ?"？

s---------------634227387532666996
Content-Disposition: form-data; name='key'

c06f4d0cdf6f2cc652635a08be34973d
X---------------634227387532666996
Content-Disposition: form-data; name='type'

file
?---------------634227387532666996
Content-Disposition: form-data; name='image'; filename='application_osx_split.png'
Content-Type=image/png

?PNG

我的代码

var bound = "-------------" + DateTime.Now.Ticks.ToString();
var tmplField = "--" + bound + "\r\nContent-Disposition: form-data; name='{0}'\r\n\r\n{1}\r\n";
var tmplFile = "--" + bound + "\r\nContent-Disposition: form-data; name='{0}'; filename='{1}'\r\nContent-Type={2}\r\n\r\n";

....

using (var reqStream = req.GetRequestStream())
{
    var reqWriter = new BinaryWriter(reqStream);

    reqWriter.Write(string.Format(tmplField, "key", "c06f4d0cdf6f2cc652635a08be34973d"));
    reqWriter.Write(string.Format(tmplField, "type", "file"));
    reqWriter.Write(string.Format(tmplFile, "image", Path.GetFileName(filepath), "image/" + Path.GetExtension(filepath).Substring(1)));
    reqWriter.Write(File.ReadAllBytes(filepath));
    reqWriter.Write("\r\n--" + bound + "--");
    reqWriter.Flush();
}

UPDATE

我注意到如果我做了类似下面的事情,使用Stream和Binary Writers的组合,我可以避免这个问题.为什么会这样？

var reqWriter = new StreamWriter(reqStream);
reqWriter.Write(string.Format(tmplField, "key", "c06f4d0cdf6f2cc652635a08be34973d"));
reqWriter.Write(string.Format(tmplField, "type", "file"));
reqWriter.Write(string.Format(tmplFile, "image", Path.GetFileName(filepath), "image/" + Path.GetExtension(filepath).Substring(1)));
reqWriter.Flush();

var binWriter = new BinaryWriter(reqStream);
binWriter.Write(File.ReadAllBytes(filepath));
binWriter.Write("\r\n--" + bound + "--");
binWriter.Flush();

Answer 1

BinaryWriter为字符串添加长度前缀.

请改用StreamWriter.