c# - 如何在我的请求 XML 中包含前导码？

Question

我正在使用 ObjectContent 构建 XML 请求，如下所示:

private HttpRequestMessage CreateRequest<T>(T content, HttpMethod method) where T : class
{
    // create http message request
    var request = CreateRequest(method);

    // set contents of the HTTP message
    var xmlFormatter = new XmlMediaTypeFormatter
                           {
                               Indent = true,
                               UseXmlSerializer = true
                           };

    var objectContent = new ObjectContent<T>(content, xmlFormatter);
    request.Content = objectContent;

    // return HttpRequestMessage
    return request;
}

这很好用!但是，输出不包括 XML 序言，例如

<?xml version="1.0" encoding="UTF-8"?>

我如何鼓励 XmlSerializer 包含该行？

Answer 1

我不知道如何用 ObjectContent 做到这一点，所以我先将它序列化，然后通过 StreamContent 将它传递给请求:

private HttpRequestMessage CreateRequest<T>(T content, HttpMethod method) where T : class
{
    var request = CreateRequest(method);
    var encoding = Encoding.UTF8;
    var xmlWriterSettings = new XmlWriterSettings { Indent = true, Encoding = encoding };

    // StringWriterWithEncoding courtesy of http://stackoverflow.com/a/9459212/29
    using (var stringWriter = new StringWriterWithEncoding(encoding))
    using (var xmlWriter = XmlWriter.Create(stringWriter, xmlWriterSettings))
    {
        var xmlSerializer = new XmlSerializer(typeof(T));
        xmlSerializer.Serialize(xmlWriter, content);
        request.Content = new StringContent(stringWriter.ToString(), encoding);
    }

    return request;
}