title: return string from multiline between two digit values in C#
body: <p>I have a string that can span multiple lines. I would like to append the string part at the end of the line. The string is between two digit values</p>
  
  <p>For example:</p>
  
  <pre><code>567899|190.78.9|xmp  
  xmyz  
  lpz  
  dwx  
  765423|195.9.0|nnox  
  wertx  
  wz  
  89021|199.6.7|xxz  
  </code></pre>
  
  <p>Desired output:</p>
  
  <pre><code>567899|190.78.9|xmp xmyz lpz dwx 
  765423|195.9.0|nnox wertx wz
  </code></pre>
  
  <p>Kindly assist on how to do this in c#.
  I tried the code below but it only prints the lines starting with digits and omits the strings in multiline</p>
  
  <pre><code>foreach (string line in File.ReadLines(path2))
  {                    
      if (Regex.IsMatch(line, @"^\d+"))
      {
          File.AppendAllText(path2 + "mfile2.txt", line + Environment.NewLine);    
      }
  }
  </code></pre>