C# .NET serialization caching-application-block

无法访问关闭的流

发布于 2024-08-22 16:36:00 字数 1131 浏览 2 评论 0原文

我正在尝试使用缓存应用程序块来缓存一些图像（这些图像需要很长时间才能渲染）

  BitmapSource bitmapSource; ///some bitmap source already created
  _cache ///  Caching Application Block
  String someId; //id for this image, used as the key for the cache

  using (var stream = new MemoryStream())
    {
        PngBitmapEncoder encoder = new PngBitmapEncoder();
        encoder.Interlace = PngInterlaceOption.On;
        encoder.Frames.Add(BitmapFrame.Create(bitmapSource));             
        encoder.Save(stream);
        _cache.Add(someId, stream);
    }

然后使用以下方式加载它们：

imStream = (Stream)_cache.GetData(someId));
if (imStream != null)
{
    PngBitmapDecoder decoder = new PngBitmapDecoder(imStream,  BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
    return decoder.Frames[0];  //return the bitmap source
}

但是在加载过程中，我在“new PngBitmapDecoder”行中收到以下异常：

“无法访问关闭的流。

我知道我在上面的代码中关闭了流，但是 _cache.Add() 不是在退出之前制作副本（通过序列化）吗？序列化流的正确过程是什么？

谢谢！

原文

I'm trying to use the Caching Application Block to cache some images (these images take a long time to render)

  BitmapSource bitmapSource; ///some bitmap source already created
  _cache ///  Caching Application Block
  String someId; //id for this image, used as the key for the cache

  using (var stream = new MemoryStream())
    {
        PngBitmapEncoder encoder = new PngBitmapEncoder();
        encoder.Interlace = PngInterlaceOption.On;
        encoder.Frames.Add(BitmapFrame.Create(bitmapSource));             
        encoder.Save(stream);
        _cache.Add(someId, stream);
    }

And then load them using:

imStream = (Stream)_cache.GetData(someId));
if (imStream != null)
{
    PngBitmapDecoder decoder = new PngBitmapDecoder(imStream,  BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
    return decoder.Frames[0];  //return the bitmap source
}

But during the load, i get the following exception at that "new PngBitmapDecoder" line:

"Cannot access a closed Stream.

I understand I closed the stream in the above code, but isn't _cache.Add() making a copy (via Serialization) before it exits? What's the correct process of serializing the stream?

THanks!

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维持三分热 2024-08-29 16:36:00

问题是流在 using 块末尾关闭（通过 Dispose()）。您保留对关闭流的引用。

相反，将流的内容保存到缓存中：

_cache.Add(someId, stream.ToArray());

当您调用 PngBitmapDecoder 构造函数时，您必须创建一个新的 MemoryStream 来从该字节数组中读取。

The problem is that the stream is closed (via Dispose()) at the end of the using block. You retain a reference to the closed stream.

Instead, save the contents of the stream to your cache:

_cache.Add(someId, stream.ToArray());

When you call the PngBitmapDecoder constructor, you'll have to create a new MemoryStream to read from that byte array.

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不再让梦枯萎 2024-08-29 16:36:00

但是 _cache.Add() 不是在退出之前创建一个副本（通过序列化）吗？

未必。如果它是“正在处理”，它将只存储对象引用；无论如何，Stream 并不是真正可序列化的（Stream 是软管，而不是桶）。

您想要存储 BLOB - 而不是 Stream：

    _cache.Add(someId, stream.ToArray());

...

byte[] blob = _cache.GetData(someId);
if(blob != null) {
    using(Stream inStream = new MemoryStream(blob)) {
         // (read)
    } 
}

but isn't _cache.Add() making a copy (via Serialization) before it exits?

Not necessarily. If it is "in process" it will just store the object reference; Stream isn't really very serializable anyway (a Stream is a hose, not a bucket).

You want to store the BLOB - not the Stream:

    _cache.Add(someId, stream.ToArray());

...

byte[] blob = _cache.GetData(someId);
if(blob != null) {
    using(Stream inStream = new MemoryStream(blob)) {
         // (read)
    } 
}

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