C＃文本文件浏览和文件写入

Question

I have this very large text file (around 35 000+ lines of information) and I would like to extract certain lines from it and place them in another text file.

The text file goes like this:

    Feature info
    Feature name: 123456
    Version: 1

    Tokens total: 35
    Tokens remaining: 10

And I'd like to extract Feature name and tokens total. What I had in mind was a form with two buttons: 1 for browsing the file and the other to do the whole reading and writing to file part, of course in the same line by line format.

Anyone have any clues on how to do it? I have searched and I haven't really found specific things, also quite new to file read/write...

EDIT

Ok here is what I have so far and it works:

private void button1_Click(object sender, EventArgs e)
    {

        int counter = 0;
        string line;
        string s1 = "Feature name";
        string s2 = "Tokens total";


        // Read the file and display it line by line.
        System.IO.StreamReader file = new System.IO.StreamReader("d:\\license.txt");
        using (System.IO.StreamWriter file2 = new System.IO.StreamWriter(@"D:\test.txt")) 
         while ((line = file.ReadLine()) != null)
          {
              if (line.Contains(s1) || line.Contains(s2))
              {
                  file2.WriteLine(line);
                  counter++;
              }
          }

        file.Close();

And this is done by a single button. What I want though is to be able to search for the file I want and then use another button in order to do all writing process

Answer 1

You can use StreamReader and StreamWriter for read/write file

To extract specific part of text, you may use Regex.Matches , it will return Match , then you can retrieve the defined group in Match.Groups

// Search name
Match mu = Regex.Match(line, @"Feature name: (\d+)");

// Get name
if (mu.Groups.Count == 1) Console.Writeline(mu.Groups[0].Value);

Answer 2

Answer for the EDIT :

You can store the read data in property or private field in the form class. Use String or StringBuilder preferably. When the second button is clicked check if there is stored data and write it to the output file.

private StringBuilder data = new StringBuilder();

private void button2_Click(object sender, EventArgs e)
{
    if(data.Length > 0)
    {
        using(System.IO.StreamWriter file2 = new System.IO.StreamWriter(@"D:\test.txt"))
        {
            file2.Write(data.ToString());
        }
    }
}

private void button1_Click(object sender, EventArgs e)
{
    // Clear the previous store data
    data.Clear();

    // ...

    System.IO.StreamReader file = new System.IO.StreamReader("d:\\license.txt"); 
    while ((line = file.ReadLine()) != null)
    {
        if (line.Contains(s1) || line.Contains(s2))
        {
            sb.AppendLine(line);
            counter++;
        }
    }

    file.Close();
}

Please add using for System.IO and surround your StreamReader and StreamWriter with using block so your code will be more readable and you won't forget to release the used resources.