Wp7上的InvalidOperationException读取XML,xml声明和doctype之间没有CR

Question

我在WP7上加载XML,我发现如果我在XML声明和doctype之间没有换行符,即使我忽略了doctype,我也会得到一个InvalidOperationException.在桌面上我没有这样的错误.

我的代码:

private static void Example()
{
    const string works =
        @"<?xml version=""1.0""?>
<!DOCTYPE example SYSTEM ""http://example.com/example.dtd""><hello></hello>";

    const string fails =
        @"<?xml version=""1.0""?><!DOCTYPE example SYSTEM ""http://example.com/example.dtd""><hello></hello>";

    var textReader = new StringReader(works);  
    var xmlReaderSettings = new XmlReaderSettings {DtdProcessing = DtdProcessing.Ignore,};
    var xmlReader = XmlReader.Create(textReader, xmlReaderSettings);
    XDocument.Load(xmlReader);  // No problem here

    textReader = new StringReader(fails);  

    xmlReader = XmlReader.Create(textReader, xmlReaderSettings);
    XDocument.Load(xmlReader);  // Fails here
}

第二个XDocument.Load失败并出现InvalidOperationException,并且消息XmlReader不应位于XmlDeclaration类型的节点上.唯一的区别是第二种情况下没有新线.

有没有人见过这个,并找到了解决方法？这适用于桌面btw - 在WP7上失败.在我的实际情况中,我正在从流中读取XML,因此在正确的位置手动注入新行并不是那么容易.

达米安

Answer 1

现在我已经实现了一个注入 NewLine 的 TextReader 包装器。我将其包含在这里，以防有人发现它有用，也以防有人有更优雅的解决方案 - 如果是这样，请发表评论！

它仅依赖于 XmlReader 调用 Read(...) 方法来读取数据 - 否则它会抛出 NotImplementedException。

在上面的示例中，您将像这样使用它：

textReader = new NewlineAfterXmlDeclReader(new StringReader(fails));  

这是实施

class NewlineAfterXmlDeclReader : TextReader
{
    private const int InitialChunkSize = 80;
    private const string SearchText = "?><!" + "DOCTYPE";  //concatenation injected for readability in SO purposes only
    private static readonly string ReplaceText = "?>" + Environment.NewLine + "<!" + "DOCTYPE";

    private readonly TextReader _wrappedReader;
    private TextReader _firstChunkReader;

    public NewlineAfterXmlDeclReader(TextReader wrappedReader)
    {
        _wrappedReader = wrappedReader;
        var initialChunk = new char[InitialChunkSize];
        var count = _wrappedReader.Read(initialChunk, 0, InitialChunkSize);
        var initialChunkString = new String(initialChunk, 0, count);

        _firstChunkReader = new StringReader(initialChunkString.Replace(SearchText, ReplaceText));
    }

    public override int Read(char[] buffer, int index, int count)
    {
        var firstChunkReadCount = 0;
        if (_firstChunkReader != null)
        {
            firstChunkReadCount = _firstChunkReader.ReadBlock(buffer, index, count);
            if (firstChunkReadCount == count) return firstChunkReadCount;
            _firstChunkReader = null;
            index += firstChunkReadCount;
            count -= firstChunkReadCount;
        }

        return firstChunkReadCount + _wrappedReader.Read(buffer, index, count);
    }

    public override void Close()
    {
        _wrappedReader.Close();
    }

    protected override void Dispose(bool disposing)
    {
        _wrappedReader.Dispose();
    }

    public override int Peek() { throw new NotImplementedException(); }
    public override int Read() { throw new NotImplementedException(); }
    public override string ReadToEnd() { throw new NotImplementedException(); }
    public override int ReadBlock(char[] buffer, int index, int count) { throw new NotImplementedException(); }
    public override string ReadLine() { throw new NotImplementedException(); }
}