Is there a C# equivalent of Java's LineNumberReader?

Is there a C# equiva开发者_Python百科lent of Java's LineNumberReader?

i.e. a StreamReader.ReadLine() which kept count of the line number. Or is the only way to achieve this by creating a custom subclass of StreamReader, and implement the necessary counting in an overridden method?

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There is no direct equivalent in the .NET Framework.

If you create a custom class, I recommend you create a class that extends TextReader and wraps a TextReader instance, so it can be used with any TextReader subclass (StreamReader, StringReader).

At a minimum, you need to override the TextReader.Read and TextReader.Peek methods. For efficiency, you should also override all the other virtual methods of the TextReader class.

class LineNumberTextReader : TextReader
{
    private readonly TextReader reader;
    private int b;
    private int line;

    public LineNumberTextReader(TextReader reader)
    {
        if (reader == null) throw new ArgumentNullException("reader");
        this.reader = reader;
    }

    public int Line
    {
        get { return this.line; }
    }

    public override int Peek()
    {
        return this.reader.Peek();
    }

    public override int Read()
    {
        int b = this.reader.Read();
        if ((this.b == '\n') || (this.b == '\r' && b != '\n')) this.line++;
        return this.b = b;
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing) this.reader.Dispose();
    }
}

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There is not such a functionality. You have to keep a local variable and increment or implement a simple StreamReader:

public class CustomStreamReader : StreamReader
{
    private int _lineNumber  = 0;

    public CustomStreamReader(Stream stream)
        : base(stream)
    {
    }

    public int LineNumber 
    { 
        get 
        {
            return _lineNumber;
        } 
    }

    public override string ReadLine()
    {
        _lineNumber++;
        return base.ReadLine();
    }
}

Bear in mind, this class assumes you only initialise it with a Stream and you will only call ReadLine(). Otherwise you have to fully override to make sure LineNumber is valid.