使用非ASCII字符过帐XML

我在试着修补 RestSharp 让它能够 POST 非ASCII字符的XML 岗位

它是怎么写的:

private void WriteRequestBody(HttpWebRequest webRequest) {
    if (HasBody) {
        webRequest.ContentLength = RequestBody.Length;

        var requestStream = webRequest.GetRequestStream();
        using (var writer = new StreamWriter(requestStream, Encoding.ASCII)) {
            writer.Write(RequestBody);
        }
    }
}

RequestBody ???

现在,我执行以下操作:

var encoding = Encoding.UTF8;

webRequest.ContentLength = encoding.GetByteCount(RequestBody);

var requestStream = webRequest.GetRequestStream();
using (var writer = new StreamWriter(requestStream, encoding)) {
    writer.Write(RequestBody);
}

但它抛出 IOException 在 Stream.Dispose() 说“在写入所有字节之前不能关闭流。”

如何发布此XML?