c# - "Object can be disposed of more than once"错误

Question

当我对以下代码块运行代码分析时，我收到此消息:

对象“stream”可以在方法“upload.Page_Load(object, EventArgs)”中处理多次。为避免生成 System.ObjectDisposedException，您不应对一个对象多次调用 Dispose。

using(var stream = File.Open(newFilename, FileMode.CreateNew))
using(var reader = new BinaryReader(file.InputStream))
using(var writer = new BinaryWriter(stream))
{
    var chunk = new byte[ChunkSize];
    Int32 count;
    while((count = reader.Read(chunk, 0, ChunkSize)) > 0)
    {
        writer.Write(chunk, 0, count);
    }
}

我不明白为什么它会被调用两次，以及如何修复它以消除错误。有帮助吗？

Answer 1

我努力解决这个问题并找到了示例 here非常有帮助。我将发布代码以供快速查看:

using (Stream stream = new FileStream("file.txt", FileMode.OpenOrCreate))
{
    using (StreamWriter writer = new StreamWriter(stream))
    {
        // Use the writer object...
    }
}

用 try/finally 替换外部 using 语句，确保在 StreamWriter 中使用流后将流清空，并在处理前检查以确保它在 finally 中不为空。

Stream stream = null;
try
{
    stream = new FileStream("file.txt", FileMode.OpenOrCreate);
    using (StreamWriter writer = new StreamWriter(stream))
    {
        stream = null;
        // Use the writer object...
    }
}
finally
{
    if(stream != null)
        stream.Dispose();
}

这样做消除了我的错误。