4.6　递归

using System.IO;

public static class LineCounter
{
// Use the first argument as the directory
// to search, or default to the current directory.
public static void Main(string[] args)
{
int totalLineCount = 0;
string directory;
if (args.Length > 0)
{
directory = args[0];
}
else
{
directory = Directory.GetCurrentDirectory();
}
totalLineCount = DirectoryCountLines(directory);
System.Console.WriteLine(totalLineCount);
}

static int DirectoryCountLines(string directory)                
{
int lineCount = 0;
foreach (string file in
Directory.GetFiles(directory, "*.cs"))
{
lineCount += CountLines(file);
}

foreach (string subdirectory in
Directory.GetDirectories(directory))
{
lineCount += DirectoryCountLines(subdirectory);        
}

return lineCount;
}

private static int CountLines(string file)
{
string line;
int lineCount = 0;
FileStream stream =
new FileStream(file, FileMode.Open);
StreamReader reader = new StreamReader(stream);
line = reader.ReadLine();

while(line != null)
{
if (line.Trim() != "")
{
lineCount++;
}
line = reader.ReadLine();
}

        reader.Close();
stream.Close();
return lineCount;
}
}

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