Asp.net MemoryStream 无法访问已关闭的流

发布于06月07日

嗨，为什么using (var sw = new StreamWriter(ms))返回Cannot access a closed Stream exception.Memory Stream在这个代码上面.

using (var ms = new MemoryStream())
{
    using (var sw = new StreamWriter(ms))
    {                 
        sw.WriteLine("data");
        sw.WriteLine("data 2");
        ms.Position = 0;
        using (var sr = new StreamReader(ms))
        {
            Console.WriteLine(sr.ReadToEnd());                        
        }
    } //error here
}

最好的解决方法是什么？

推荐答案

这是因为StreamReader在被处理时会自动关闭底层流.using语句会自动执行此操作.

但是，您正在使用的StreamWriter仍在try 处理流(此外，编写器的using语句现在正在try 处理StreamWriter，然后它将try 关闭流).

解决这个问题的最好方法是:不要使用using，也不要丢弃StreamReader和StreamWriter.请参见this question.

using (var ms = new MemoryStream())
{
    var sw = new StreamWriter(ms);
    var sr = new StreamReader(ms);

    sw.WriteLine("data");
    sw.WriteLine("data 2");
    ms.Position = 0;

    Console.WriteLine(sr.ReadToEnd());                        
}

如果您对sw和sr被垃圾收集而没有在代码中处理(如建议的那样)感到不安，您可以这样做:

StreamWriter sw = null;
StreamReader sr = null;

try
{
    using (var ms = new MemoryStream())
    {
        sw = new StreamWriter(ms);
        sr = new StreamReader(ms);

        sw.WriteLine("data");
        sw.WriteLine("data 2");
        ms.Position = 0;

        Console.WriteLine(sr.ReadToEnd());                        
    }
}
finally
{
    if (sw != null) sw.Dispose();
    if (sr != null) sr.Dispose();
}