如何处理MemoryStream对象
本文关键字:MemoryStream 对象 处理 何处理 | 更新日期: 2023-09-27 18:20:52
以下代码用于将现有PDF缝合在一起[顺便说一句,我们使用TallComponents进行实际缝合,以防您想知道PDFUtility
是什么]:
PDFUtility.Document docFinal = new PDFUtility.Document();
PDFUtility.Document docToAdd = null;
byte[] combinedFile;
foreach (byte[] content in fileContents)
{
MemoryStream fileContentStream = new MemoryStream(content);
docToAdd = new PDFUtility.Document(fileContentStream);
docFinal.Pages.AddRange(docToAdd.Pages.CloneToArray());
}
using (MemoryStream stream = new MemoryStream())
{
docFinal.Write(stream);
combinedFile = stream.ToArray();
}
这个代码的明显问题是这个命令:
MemoryStream fileContentStream = new MemoryStream(content);
内存流fileContentStream
没有被处理,可能(我相信)占用资源的时间超过了需要的时间。
显而易见的解决方案是将MemoryStream的创建封装在using
块中。代码看起来是这样的:
PDFUtility.Document docFinal = new PDFUtility.Document();
PDFUtility.Document docToAdd = null;
byte[] combinedFile;
foreach (byte[] content in fileContents)
{
using (MemoryStream stream = new MemoryStream())
{
MemoryStream fileContentStream = new MemoryStream(content);
docToAdd = new PDFUtility.Document(fileContentStream);
docFinal.Pages.AddRange(docToAdd.Pages.CloneToArray());
}
}
using (MemoryStream stream = new MemoryStream())
{
docFinal.Write(stream);
combinedFile = stream.ToArray();
}
使用上述代码中的using块会导致代码在这一行失败(因为流之前已被处理):
docFinal.Write(stream);
一种可能的解决方案是跟踪所有MemoryStream实例,并在使用完毕后将其处理掉。这是它的代码:
PDFUtility.Document docFinal = new PDFUtility.Document();
PDFUtility.Document docToAdd = byte[] combinedFile;
List<MemoryStream> streams = new List<MemoryStream>();
foreach (byte[] content in fileContents)
{
MemoryStream fileContentStream = new MemoryStream(content);
streams.Add(fileContentStream); //EACH INSTANCE OF A STREAM IS TRACKED
docToAdd = new PDFUtility.Document(fileContentStream);
docFinal.Pages.AddRange(docToAdd.Pages.CloneToArray());
}
using (MemoryStream stream = new MemoryStream())
{
docFinal.Write(stream);
combinedFile = stream.ToArray();
}
streams.ForEach(s => s.Dispose()); //DISPOSE OF ALL STREAMS HERE
上面的代码有效。我只是将Dispose延迟到最终文档写出之后。
然而,这似乎不是"最佳"解决方案。有没有任何方法可以使用块来实现(从而保证对象得到正确处理?
using
块对于try-finally
块来说只不过是语法糖。
根据using块的使用方式,您最终会得到两种类型的try-filly块。
案例1:
// This code ...
using( var thing = new Thing() ) {
thing.DoOperation();
}
// ... turns into this scoped try-finally:
{
var thing = new Thing();
try {
thing.DoOperation();
}
finally {
thing.Dispose();
thing = null;
}
}
案例二:
// This code ...
var thing = new Thing();
using( thing ) {
thing.DoOperation();
}
// ... turns into this code
var thing = new Thing();
try {
thing.DoOperation();
}
finally {
thing.Dispose();
// Note the lack of a null assignment.
}
有了这些知识,您可以修改第三个解决方案,使其使用finally
块,以确保始终清理MemoryStream
对象。
PDFUtility.Document docFinal = new PDFUtility.Document();
PDFUtility.Document docToAdd = byte[] combinedFile;
List<MemoryStream> streams = new List<MemoryStream>();
try
{
foreach (byte[] content in fileContents)
{
MemoryStream fileContentStream = new MemoryStream(content);
streams.Add(fileContentStream); //EACH INSTANCE OF A STREAM IS TRACKED
docToAdd = new PDFUtility.Document(fileContentStream);
docFinal.Pages.AddRange(docToAdd.Pages.CloneToArray());
}
using (MemoryStream stream = new MemoryStream())
{
docFinal.Write(stream);
combinedFile = stream.ToArray();
}
}
finally
{
streams.ForEach(s => s.Dispose()); //DISPOSE OF ALL STREAMS HERE
}