使用foreach简化文本文件的访问。

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很多时候,我们总是按照行的方式访问文本文件,使用foreach语句能够极大地简化访问逻辑:例如:

foreach (string line in new LineReader(”c:\abc.txt”))
  Console.WriteLine(line);

完整代码如下:

using System;

using System.IO;

using System.Text;

using System.Collections;

 

namespace Forks.Utils.IO

{

    public struct LineReader : IDisposable

    {

    public LineReader(string file, Encoding encoding) : this(file, encoding, false)

        {

    }

 

    public LineReader(string file, Encoding encoding, bool ignoreBlankLines) : this(new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read), encoding, ignoreBlankLines)

    {

    }

 

    public LineReader(Stream stream, Encoding encoding) : this(stream, encoding, false)

    {

    }

 

    public LineReader(Stream stream, Encoding encoding, bool ignoreBlankLines) : this(new StreamReader(stream, encoding), ignoreBlankLines)

    {

    }

 

    public LineReader(TextReader reader) : this(reader, false)

    {

    }

 

    TextReader mReader;

    bool mIgnoreBlankLines;

 

    public LineReader(TextReader reader, bool ignoreBlankLines)

    {

      mReader = reader;

      mIgnoreBlankLines = ignoreBlankLines;

      mCurrent = null;

    }

 

    public LineReader GetEnumerator()

    {

      return this;

    }

 

    public void Reset()

    {

      throw new NotSupportedException("LineReaderÖ»ÄܶÁÈ¡Ò»´Î");

    }

 

    string mCurrent;

    public string Current

    {

      get

      {

        return mCurrent;

      }

    }

 

    public bool MoveNext()

    {

      do

      {

        mCurrent = mReader.ReadLine();

      }while (mIgnoreBlankLines && mCurrent != null && mCurrent.Length == 0);

      return mCurrent != null;

    }

 

    public void Dispose()

    {

      mReader.Close();

    }

  }

}

 

测试代码:

using System;

using System.IO;

using System.Text;

 

using NUnit.Framework;

 

using Forks.Test;

 

namespace Forks.Utils.IO

{

  [TestFixture]

    public class LineReaderTest

    {

    const string TestLines = @"abc asd ewr afa e

  start with blanks

end with blanks  

ºº×Öabc123!@#

 

end of text!";

 

    [Test]

    public void ReadFromReader()

    {

      doTest(new LineReader(new StringReader(TestLines)));

    }

 

    [Test]

    public void ReadFromFile()

    {

      string file = Path.GetTempFileName();

      try

      {

        StringUtil.SaveToFile(TestLines, file, Encoding.GetEncoding("gb2312"));

 

        doTest(new LineReader(file, Encoding.GetEncoding("gb2312")));

      }

      finally

      {

        FileUtil.SafeDelete(file);

      }

    }

 

    [Test]

    public void ReadFromStream()

    {

      string file = Path.GetTempFileName();

      try

      {

        StringUtil.SaveToFile(TestLines, file, Encoding.GetEncoding("gb2312"));

 

        using (Stream stream = new FileStream(file, FileMode.Open))

          doTest(new LineReader(stream, Encoding.GetEncoding("gb2312")));

      }

      finally

      {

        FileUtil.SafeDelete(file);

      }

    }

 

    void doTest(LineReader reader)

    {

      StringBuilder sb = new StringBuilder();

      foreach (string line in reader)

        sb.Append(line + Environment.NewLine);

 

      Assert.AreEqual(TestLines + Environment.NewLine, sb.ToString());

    }

 

    [Test]

    public void IgnoreBlankLine()

    {

      foreach (string line in new LineReader(new StringReader(TestLines), true))

        Assert.IsTrue(line.Length != 0);

    }

    }

}

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