无法访问已关闭的 Stream？

Question

我刚刚在我的代码中遇到了一个错误，它打开了文件并读取了 rawData。

我得到的错误如下：

如您所见，我正在打开一个内存流，但在这样做时我收到一条错误消息，提示我无法访问该流？

我无法访问关闭的流有什么原因吗？

使用的代码：

// Try to decompress the file data.
byte[] rawData = null;

using (MemoryStream zipStream = new MemoryStream(fileData))
{
    if (ZipPackage.IsZipFile(zipStream))
    {
        using (ZipPackage unzipper = ZipPackage.Open(zipStream))
        {
            // The zip package only contains one entry since GeoObject.FileData only contains one shape or POI.
            if (unzipper.ZipPackageEntries.Count > 0)
            {
                StreamReader reader = new StreamReader(unzipper.ZipPackageEntries[0].OpenInputStream());
                rawData = System.Text.Encoding.UTF8.GetBytes(reader.ReadToEnd());
            }
        }
    }
}

堆栈

at System.IO.__Error.StreamIsClosed()
at System.IO.MemoryStream.set_Position(Int64 value)
at Telerik.Windows.Zip.ZipPackage.IsZipFile(Stream stream)
at Satmap.Planner.Silverlight.XmlConverters.DBGeoObjectsToFromDBShapes.ExtractRawFileData(GeoObject geoObject, Byte[] fileData)
at Satmap.Planner.Silverlight.DatabaseShapesToFromMapShapes.ConvertDatabaseShapesToMapShapes(GeoObject geoObject, Boolean filter)
at Satmap.Planner.Silverlight.DatabaseShapesToFromMapShapes.ConvertDatabaseShapesToMapShapes(GeoObject geoObject)
at Satmap.Planner.Silverlight.ViewControllers.MainMapViewController.BackgroundWorkerFileLoad_RunWorkerCompleted(Object sender, RunWorkerCompletedEventArgs e)
at System.ComponentModel.BackgroundWorker.OnRunWorkerCompleted(RunWorkerCompletedEventArgs e)
at System.ComponentModel.BackgroundWorker.<OnRun>b__1(Object state) 

新堆栈：

at System.IO.MemoryStream.set_Capacity(Int32 value)
at System.IO.MemoryStream.EnsureCapacity(Int32 value)
at System.IO.MemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count)
at System.IO.Stream.InternalCopyTo(Stream destination, Int32 bufferSize)
at System.IO.Stream.CopyTo(Stream destination)
at Telerik.Windows.Zip.ZipArchive.WriteArchive()
at Telerik.Windows.Zip.ZipArchive.Dispose(Boolean disposing)
at Telerik.Windows.Zip.ZipArchive.Dispose()
at Satmap.Planner.Silverlight.XmlConverters.DBGeoObjectsToFromDBShapes.ExtractRawFileData(GeoObject geoObject, Byte[] fileData)
at Satmap.Planner.Silverlight.DatabaseShapesToFromMapShapes.ConvertDatabaseShapesToMapShapes(GeoObject geoObject, Boolean filter)
at Satmap.Planner.Silverlight.DatabaseShapesToFromMapShapes.ConvertDatabaseShapesToMapShapes(GeoObject geoObject)
at Satmap.Planner.Silverlight.ViewControllers.MainMapViewController.BackgroundWorkerFileLoad_RunWorkerCompleted(Object sender, RunWorkerCompletedEventArgs e)
at System.ComponentModel.BackgroundWorker.OnRunWorkerCompleted(RunWorkerCompletedEventArgs e)
at System.ComponentModel.BackgroundWorker.<OnRun>b__1(Object state)

Answer 1

您在这里看到的是 Telerik ZipPackage 类的行为。静态 IsZipFile 方法正在处理流，可能是由于一个错误（您可以联系 Telerik 支持）。

但是，您可能没有必要首先检查 zip 包的有效性。只需在相关代码周围使用try...catch：

// Try to decompress the file data.
byte[] rawData = null;

using (MemoryStream zipStream = new MemoryStream(fileData))
{
    try
    {
        using (ZipPackage unzipper = ZipPackage.Open(zipStream))
        {
            // The zip package only contains one entry since GeoObject.FileData only contains one shape or POI.
            if (unzipper.ZipPackageEntries.Count > 0)
            {
                StreamReader reader = new StreamReader(unzipper.ZipPackageEntries[0].OpenInputStream());
                rawData = System.Text.Encoding.UTF8.GetBytes(reader.ReadToEnd());
            }
        }
    }
    catch (Exception ex)
    {
         // ZipPackage throws an exception of type Exception if the 
         // package is not valid. Handle exception here, e.g. log etc
    }
}

更新

Telerik 的 ZipArchive 类似乎是一只奇怪的野兽。如果您使用的是 .NET 4.5 或更高版本，则最好切换到 System.IO.Compression.ZipArchive 类。如果没有，您可以通过不从固定数组创建内存流来解决不可扩展内存流的问题。你可以使用 new MemoryStream(fileData) 而不是：

using (var zipStream = new MemoryStream())
{
    zipStream.Write(fileData, 0, fileData.Length);
    zipStream.Position = 0;

    // continue here
}