C# How to add string elements in array to string

Question

Hello to all. Need assistance to do this. Or advice about how to add string to string elements in array?

1. We have 2 txt files with 100 or more strings in each:

   domain.txt
   domain1
   domain2
   ..
   title.txt
   title1
   tilte2
   ..

2. and we have:

   string link = < a h ref="http://www.domain.com" target="_blank">title< /a>

3. After reading files we would have 2 string arrays - we need to replace domain.com with each string from domain.txt and title with each string from title.txt like this:

   < a h ref="http://www.domain1.com" target="_blank">title1< /a>
   < a h ref="http://www.domain2.com" target="_blank">title2< /a>
   ..

4. Save the result string array into 2 txt files in that way: from 1-50 strings to
   1.txt and from 50-100 to 2.txt file

What is the best way to do this by manipulating strings with strings array elements?

Answer 1

This is probably the simplest way to read the files:

    string[] domains = File.ReadAllLines("domain.txt");
    string[] titles = File.ReadAllLines("titles.txt");

To make the substitutions you can use string.Format:

    int n = domains.Length;
    string[] results = new string[n];

    for (int i = 0; i < n; ++i)
    {
        results[i] = string.Format(
            @"<a href=""http://{0}"" target=""_blank"">{1}</a>",
            domains[i], titles[i]);
    }

To write the output you can use Linq:

    File.WriteAllLines("file1.txt", results.Take(n / 2).ToArray());
    File.WriteAllLines("file2.txt", results.Skip(n / 2).ToArray());

If your template is a paramter you might want to construct the format string dynamically rather than hardcoding it. Here is an example of how you could do that:

using System;
using System.IO;
using System.Linq;

class Program
{
    static string escapeBraces(string s)
    {
        return s.Replace("{", "{{").Replace("}", "}}");
    }

    static string createFormatString(string template, params string[] parameters)
    {
        template = escapeBraces(template);

        for (int i =0; i < parameters.Length; ++i) {
            template = template.Replace(
                escapeBraces(parameters[i]),
                "{" + i + "}");
        }

        return template;
    }

    static void Main(string[] args)
    {
        string template = @"<a {}href=""http://www.domain.com"" target=""_blank"">title</a>";
        string formatString = createFormatString(template, "www.domain.com", "title");

        string[] domains = File.ReadAllLines("domain.txt");
        string[] titles = File.ReadAllLines("title.txt");

        int n = domains.Length;
        if (titles.Length != n)
            throw new InvalidDataException("There must be the same number domains and titles.");

        string[] results = new string[n];
        for (int i = 0; i < n; ++i)
        {
            results[i] = string.Format(formatString, domains[i], titles[i]);
        }

        File.WriteAllLines("file1.txt", results.Take(n / 2).ToArray());
        File.WriteAllLines("file2.txt", results.Skip(n / 2).ToArray());
    }
}

Answer 2

This is beautiful using LINQ and some nice methods from File:

string[] domains = File.ReadAllLines(@"C:/domains.txt");
string[] titles = File.ReadAllLines(@"C:/titles.txt");
if(domains.Length != titles.Length) { throw new InvalidOperationException(); }
string link = "<a href=\"http://www.{0}.com\" target=\"_blank\">{1}</a>";
var results = domains.Select((domain, i) => String.Format(link, domain, titles[i]));
File.WriteAllLines("results1.txt", results.Take(results.Length / 2).ToArray());
File.WriteAllLines("results2.txt", results.Skip(results.Length / 2).ToArray());

It isn't clear what you want if there are more than one-hundred domain/title pairs so I split them in half.

Answer 3

Another way is to do it lazily like this:

     static IEnumerable<string> ReadLinesLazily(string file)
 {
  using (var reader = new StreamReader(file))
  {
   string line = null;
   while ((line = reader.ReadLine()) != null)
   {
    yield return line;
   }
  }
 }

 static void Combine()
 {
  const string link = "<a href=\"{0}\">{1}</a>";
  var links = ReadLinesLazily("domains.txt").Zip(ReadLinesLazily("titels.txt"), (d, t) => String.Format(link, d, t))
  // write links here
 }