我正在尝试序列化和压缩 WPF FlowDocument
,然后执行相反的操作 - 解压缩字节数组并反序列化以重新创建 FlowDocument - 使用 .NET GZipStream
类(class)。我正在按照 MSDN 上描述的示例进行操作,并且我有以下测试程序:
var flowDocumentIn = new FlowDocument();
flowDocumentIn.Blocks.Add(new Paragraph(new Run("Hello")));
Debug.WriteLine("Compress");
byte[] compressedData;
using (var uncompressed = new MemoryStream())
{
XamlWriter.Save(flowDocumentIn, uncompressed);
uncompressed.Position = 0;
using (var compressed = new MemoryStream())
using (var compressor = new GZipStream(compressed, CompressionMode.Compress))
{
Debug.WriteLine(" uncompressed.Length: " + uncompressed.Length);
uncompressed.CopyTo(compressor);
Debug.WriteLine(" compressed.Length: " + compressed.Length);
compressedData = compressed.ToArray();
}
}
Debug.WriteLine("Decompress");
FlowDocument flowDocumentOut;
using (var compressed = new MemoryStream(compressedData))
using (var uncompressed = new MemoryStream())
using (var decompressor = new GZipStream(compressed, CompressionMode.Decompress))
{
Debug.WriteLine(" compressed.Length: " + compressed.Length);
decompressor.CopyTo(uncompressed);
Debug.WriteLine(" uncompressed.Length: " + uncompressed.Length);
flowDocumentOut = (FlowDocument) XamlReader.Load(uncompressed);
}
Assert.AreEqual(flowDocumentIn, flowDocumentOut);
但是我在 XamlReader.Load
行遇到异常,这是正常的,因为调试输出表明未压缩流的长度为零。
Compress
uncompressed.Length: 123
compressed.Length: 202
Decompress
compressed.Length: 202
uncompressed.Length: 0
为什么最终的未压缩
流不包含原始的 123 个字节?
(请忽略“压缩”字节数组比“未压缩”字节数组大的事实——我通常会处理更大的流文档)
最佳答案
在从内存流中获取压缩字节之前,您需要关闭GZipStream
。在这种情况下,关闭由因使用而调用的 Dispose
处理。
using (var compressed = new MemoryStream())
{
using (var compressor = new GZipStream(compressed, CompressionMode.Compress))
{
uncompressed.CopyTo(compressor);
}
// Get the compressed bytes only after closing the GZipStream
compressedBytes = compressed.ToArray();
}
这行得通,您甚至可以删除 MemoryStream
的 using
,因为它将由 GZipStream
处理,除非您使用构造函数重载这允许您指定底层流应该保持打开状态。这意味着您正在使用该代码在已处置的流上调用 ToArray
但这是允许的,因为字节仍然可用,这使得处置内存流有点奇怪,但如果您不这样做,FXCop 会惹恼您.
关于c# - .NET GZipStream 解压缩生成空流,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11915612/