static async Task <bool> P_TryRecognizeStreamContentAsXmlAsync(Stream stream, XmlReaderSettings xmlReaderSettings)
{
stream.EnsureNotNull(nameof(stream));
xmlReaderSettings.EnsureNotNull(nameof(xmlReaderSettings));
//
if (stream.CanSeek)
{
var xmlReader = default(XmlReader);
var textReader = default(TextReader);
var initialInputStreamPosition = default(long?);
var tryException = default(Exception);
try {
Func <Stream, bool, TextReader> createTextReader =
(locInputStream, locLeaveInputStreamOpen)
=>
new StreamReader(
stream: locInputStream,
encoding: Encoding.UTF8,
detectEncodingFromByteOrderMarks: true,
bufferSize: TextReaderWriterUtilities.DefaultBufferSize,
leaveOpen: locLeaveInputStreamOpen);
//
initialInputStreamPosition = stream.Position;
textReader = createTextReader(stream, true);
var xmlReaderSettingsClone = xmlReaderSettings.Clone();
xmlReaderSettingsClone.DtdProcessing = DtdProcessing.Prohibit;
xmlReaderSettingsClone.CloseInput = false;
xmlReaderSettingsClone.IgnoreComments
= xmlReaderSettingsClone.IgnoreProcessingInstructions
= xmlReaderSettingsClone.IgnoreWhitespace
= true;
xmlReader = XmlReader.Create(textReader, xmlReaderSettingsClone);
//
bool isXml;
try {
isXml =
await
xmlReader
.ReadAsync()
.ConfigureAwait(false);
isXml = isXml && xmlReader.NodeType == XmlNodeType.XmlDeclaration;
//
stream.Position = initialInputStreamPosition.Value;
initialInputStreamPosition = null;
}
catch (XmlException) {
isXml = false;
}
//
textReader.Dispose();
(xmlReader as IDisposable)?.Dispose();
//
return(isXml);
}
catch (Exception firstException) {
tryException = firstException;
throw;
}
finally {
try {
if (initialInputStreamPosition.HasValue)
{
try { stream.Position = initialInputStreamPosition.Value; }
catch (ObjectDisposedException) { }
}
if (tryException != null)
{
textReader?.Dispose();
(xmlReader as IDisposable)?.Dispose();
}
}
catch (Exception firstException) {
if (tryException == null)
{
throw;
}
else
{
throw tryException.ToAggregateException(firstException);
}
}
}
}
else
{
return(false);
}
}