c# 从许多文件中读取并将其中的一部分写入新文件

Question

I've try to read many files one by one and write just part of them into new file. I am new in c#, can someone give me some idea, how to do it.

Here is the code, but in this way only record all files in one main file. I want to get some information with substring from all file, and write this information to main file

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApp2
    {
    class Program
    {
        static void Main(string[] args)
        {
            string path = @"C:\Users\Name\Desktop\Files\";
            string[] files = Directory.GetFiles(path, "*", SearchOption.AllDirectories);
            using (var output = File.Create(path + "output.txt"))
            {
                foreach (var file in files)
                {
                    using (var data = File.OpenRead(file))
                    {
                        data.CopyTo(output);
                    }
                }

            }
        }
    }
}

Answer 1

You can do it like this for example if you want to use Substring :

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            string path = @"C:\Users\Name\Desktop\Files\";

            string[] files = Directory.GetFiles(path, "*", SearchOption.AllDirectories);

            //Reads the first lines
            var firstLines = files.Select(f => File.ReadLines(f).First());

            //Cuts from the fifth character and then five characters long
            //Writes the result to the file output.txt
            File.WriteAllLines(path + "\\output.txt", firstLines.Select(l => l.Substring(5, 5)));
        }
    }
}

But you can also use other string manipulation methods like Replace .