title: How to overwrite next line after found line in text document
body: <p>here I want one thing, so I take line from some value, found it in text document and now I want overwrite X not over the found line, but over the next line coming after this found line</p>
  
  <p>so if content is: </p>
  
  <pre><code>line1
  line2
  line3
  line4
  </code></pre>
  
  <p>and if <code>string text = "line2";</code> with this code:</p>
  
  <pre><code>using System;
  using System.IO;
  
  namespace _03_0
  {
      class Program
      {
          static void Main(string[] args)
          {
              string text = "line2";
  
              string text = File.ReadAllText("doc.txt"); 
              text = text.Replace(text, "X"); 
              File.WriteAllText("doc.txt", text);          
          }
      }
  }
  </code></pre>
  
  <p>I have this result:</p>
  
  <pre><code>line1
  X
  line3
  line4
  </code></pre>
  
  <p>but I want this result:</p>
  
  <pre><code>line1
  line2 
  X
  line4
  </code></pre>