我试图序列化和压缩一个
WPF
FlowDocument,然后反向解压缩字节数组并反序列化以重新创建FlowDocument – 使用.NET
GZipStream类.我正在跟踪MSDN上描述的示例,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);
然而,我在XamlReader.Load行中收到异常,这是正常的,因为调试输出告诉未压缩的流具有零长度.
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”字节数组大于“未压缩”字节数组的事实 – 我通常会使用更大的流程文档)
解决方法
在从内存流获取压缩字节之前,需要关闭GZipStream.在这种情况下,由于使用所调用的Dispose处理关闭.
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();
}
这可以工作,甚至可以删除MemoryStream的使用,因为它将由GZipStream处理,除非您使用构造函数重载,允许您指定底层流应该保持打开状态.这意味着与代码一样,您调用ToArray处理的流,但这是允许的,因为这些字节仍然可用,这使得处理内存流有点奇怪,但如果你不这样做,FXCop会让你烦恼.
