c# - 跟踪大型 XML 文件的加载进度

Question

我尝试在 dotnet(C#，框架 3.5 SP1)中跟踪大型 XML 文件(我不是这些文件的提供者)的加载进度:通过网络文件共享从 1 MB 到 300 MB。

我使用 XmlReader 进行加载，而不是直接使用 XmlDocument.Load 方法来加快加载过程。

顺便说一下，我在互联网/文档上找不到任何关于如何跟踪此加载进度的地方:似乎不存在委托(delegate)/事件。有什么办法可以执行此任务吗？拥有用于 XML 保存目的的那种功能可能是件好事。

谢谢

Answer 1

假设您正在从流中读取，这里有一个(不完美的)示例来说明如何做到这一点...基本上，ProgressStreamWrapper 包装文件流并在 Position 更改时引发事件。

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Reading big file...");

        FileStream fileStream = File.OpenRead("c:\\temp\\bigfile.xml");
        ProgressStreamWrapper progressStreamWrapper = new ProgressStreamWrapper(fileStream);
        progressStreamWrapper.PositionChanged += (o, ea) => Console.WriteLine((double) progressStreamWrapper.Position / progressStreamWrapper.Length * 100 + "% complete");
        XmlReader xmlReader = XmlReader.Create(progressStreamWrapper);

        while (xmlReader.Read())
        {
            //read the xml document
        }

        Console.WriteLine("DONE");
        Console.ReadLine();
    }
}


public class ProgressStreamWrapper : Stream, IDisposable
{
    public ProgressStreamWrapper(Stream innerStream)
    {
        InnerStream = innerStream;
    }

    public Stream InnerStream { get; private set; }

    public override void Close()
    {
        InnerStream.Close();
    }

    void IDisposable.Dispose()
    {
        base.Dispose();
        InnerStream.Dispose();
    }

    public override void Flush()
    {
        InnerStream.Flush();
    }

    public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
    {
        return InnerStream.BeginRead(buffer, offset, count, callback, state);
    }

    public override int EndRead(IAsyncResult asyncResult)
    {
        int endRead = InnerStream.EndRead(asyncResult);
        OnPositionChanged();
        return endRead;
    }

    public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
    {
        return InnerStream.BeginWrite(buffer, offset, count, callback, state);
    }

    public override void EndWrite(IAsyncResult asyncResult)
    {
        InnerStream.EndWrite(asyncResult);
        OnPositionChanged(); ;
    }

    public override long Seek(long offset, SeekOrigin origin)
    {
        long seek = InnerStream.Seek(offset, origin);
        OnPositionChanged();
        return seek;
    }

    public override void SetLength(long value)
    {
        InnerStream.SetLength(value);
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        int read = InnerStream.Read(buffer, offset, count);
        OnPositionChanged();
        return read;
    }

    public override int ReadByte()
    {
        int readByte = InnerStream.ReadByte();
        OnPositionChanged();
        return readByte;
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        InnerStream.Write(buffer, offset, count);
        OnPositionChanged();
    }

    public override void WriteByte(byte value)
    {
        InnerStream.WriteByte(value);
        OnPositionChanged();
    }

    public override bool CanRead
    {
        get { return InnerStream.CanRead; }
    }

    public override bool CanSeek
    {
        get { return InnerStream.CanSeek; }
    }

    public override bool CanTimeout
    {
        get { return InnerStream.CanTimeout; }
    }

    public override bool CanWrite
    {
        get { return InnerStream.CanWrite; }
    }

    public override long Length
    {
        get { return InnerStream.Length; }
    }

    public override long Position
    {
        get { return InnerStream.Position; }
        set
        {
            InnerStream.Position = value;
            OnPositionChanged();
        }
    }

    public event EventHandler PositionChanged;

    protected virtual void OnPositionChanged()
    {
        if (PositionChanged != null)
        {
            PositionChanged(this, EventArgs.Empty);
        }
    }

    public override int ReadTimeout
    {
        get { return InnerStream.ReadTimeout; }
        set { InnerStream.ReadTimeout = value; }
    }

    public override int WriteTimeout
    {
        get { return InnerStream.WriteTimeout; }
        set { InnerStream.WriteTimeout = value; }
    }
}