使用foreach简化文本文件的访问。

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);
}
}
}