C#/BinaryWriter：输出流中出现奇怪字符

问题描述

我很难弄清楚是什么原因导致奇怪的字符出现在我的输出流中.完整代码@pastebin

Fiddler输出

注意到我的边界前面的"s"、"X"、"�"吗？

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 + "
Content-Disposition: form-data; name='{0}'

{1}
";
var tmplFile = "--" + bound + "
Content-Disposition: form-data; name='{0}'; filename='{1}'
Content-Type={2}

";

....

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("
--" + bound + "--");
    reqWriter.Flush();
}

更新

我注意到，如果我改为使用Stream&；二进制编写器的组合进行如下操作，我就可以避免这个问题。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("
--" + bound + "--");
binWriter.Flush();

推荐答案

BinaryWriter为字符串添加长度前缀。

改用StreamWriter。

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