.net - "ReadElementContentAsBase64 method is not supported on this XmlReader"

Question

using System.IO;
using System.Runtime.Serialization;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;

namespace XmlTest
{
    class TestClass : IXmlSerializable
    {
        public XmlSchema GetSchema()
        {
            return null;
        }

        public void ReadXml(XmlReader reader)
        {
            var data = new byte[3];
            reader.ReadStartElement();
            reader.ReadElementContentAsBase64(data, 0, data.Length);
        }

        public void WriteXml(XmlWriter writer)
        {
            var data = new byte[] { 1, 2, 3 };
            writer.WriteBase64(data, 0, data.Length);
        }

        public static void Main()
        {
            var serializer = new DataContractSerializer(typeof(TestClass));

            var stringWriter = new StringWriter();
            using (var writer = XmlWriter.Create(stringWriter))
            {
                serializer.WriteObject(writer, new TestClass());
            }

            var stringReader = new StringReader(stringWriter.ToString());
            using (var reader = XmlReader.Create(stringReader))
            {
                serializer.ReadObject(reader, true);
            }
        }
    }
}

ReadElementContentAsBase64 行抛出 NotSupportedException 并显示消息:

ReadElementContentAsBase64 method is not supported on this XmlReader. Use CanReadBinaryContent property to find out if a reader implements it.

(我检查过，CanReadBinaryContent 返回 true)

我正在使用 Microsoft .NET 3.5 框架实现。

什么可能导致这种情况？

注意:我有意将 DataContractSerializer 与 IXmlSerialized 混合在一起。我意识到 DataContractSerializer 更常见的方法是将我的类设为 [DataContract]。

编辑:我现在正在使用解决方法:
Convert.FromBase64String(reader.ReadElementContentAsString())
不过，我想知道为什么常规方法会失败。

Answer 1

我也遇到这个问题了。 linq 的 doc.CreateReader() 创建的 XmlReader 没有实现 Base64 解码。我通过首先保存到 MemoryStream 并从中创建 XmlReader 来解决这个问题:

     Stream s = new MemoryStream();
     XmlSerializer serializer = new XmlSerializer(typeof(SerializableDocument));   
     document.Save(s);
     s.Seek(0, SeekOrigin.Begin);

     using (XmlReader newReader = XmlReader.Create(s))
     {
        SerializableDocument serializableDocument = (SerializableDocument)serializer.Deserialize(newReader);
        // do stuff with it
     }