StreamReader和寻求 [英] StreamReader and seeking

问题描述

您可以使用streamreader读取正常的文本文件，然后在读取过程中保存当前位置后关闭streamreader，然后再次打开streamreader并开始从该位置读取吗？

can you use streamreader to read a normal textfile and then in the middle of reading close the streamreader after saving the current position and then open streamreader again and start reading from that poision ?

如果不是这样，我还能在不锁定文件的情况下完成相同的情况吗？

if not what else can i use to accomplish the same case without locking the file ?

类似这样的东西：

 var fs = File.Open(@"C:\testfile.txt", FileMode.Open, FileAccess.Read);
        var sr = new StreamReader(fs);
        Debug.WriteLine(sr.ReadLine());//Prints:firstline
        var pos = fs.Position;
        while (!sr.EndOfStream)
        {
            Debug.WriteLine(sr.ReadLine());
        }
        fs.Seek(pos, SeekOrigin.Begin);
        Debug.WriteLine(sr.ReadLine());//Prints Nothing, i expect it to print SecondLine.

---

@lasseespeholt

---

@lasseespeholt

这是我尝试过的代码

            var position = -1;
        StreamReaderSE sr = new StreamReaderSE(@"c:\testfile.txt");
        Debug.WriteLine(sr.ReadLine());
        position = sr.BytesRead;
        Debug.WriteLine(sr.ReadLine());
        Debug.WriteLine(sr.ReadLine());
        Debug.WriteLine(sr.ReadLine());
        Debug.WriteLine(sr.ReadLine());
        Debug.WriteLine("Wait");
        sr.BaseStream.Seek(position, SeekOrigin.Begin);
        Debug.WriteLine(sr.ReadLine());

推荐答案

是的，可以看到：

var sr = new StreamReader("test.txt");
sr.BaseStream.Seek(2, SeekOrigin.Begin); // Check sr.BaseStream.CanSeek first

更新：
请注意，不必将 sr.BaseStream.Position 用于任何有用的东西，因为 StreamReader 使用缓冲区，因此它不会反映您实际阅读的内容。我想您会找不到真正的位置。因为您不能只计算字符（不同的编码以及因此的字符长度）。我认为最好的方法是使用 FileStream 本身。

Update: Be aware that you can't necessarily use sr.BaseStream.Position to anything useful because StreamReader uses buffers so it will not reflect what you actually have read. I guess you gonna have problems finding the true position. Because you can't just count characters (different encodings and therefore character lengths). I think the best way is to work with FileStream´s themselves.

更新：
从此处使用 TGREER.myStreamReader ：
http://www.daniweb.com/software-development/csharp/ thread / 35078
此类添加了 BytesRead 等。（与 ReadLine（）一起使用，显然不使用其他读取方法）
，然后您可以这样：

Update: Use the TGREER.myStreamReader from here: http://www.daniweb.com/software-development/csharp/threads/35078 this class adds BytesRead etc. (works with ReadLine() but apparently not with other reads methods) and then you can do like this:

File.WriteAllText("test.txt", "1234\n56789");

long position = -1;

using (var sr = new myStreamReader("test.txt"))
{
    Console.WriteLine(sr.ReadLine());

    position = sr.BytesRead;
}

Console.WriteLine("Wait");

using (var sr = new myStreamReader("test.txt"))
{
    sr.BaseStream.Seek(position, SeekOrigin.Begin);
    Console.WriteLine(sr.ReadToEnd());
}

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