title: String Manipulation from "[1_5],[1_3],[1_5]" to "5,3,5"
body: <p>I have the a string in below format </p>
  
  <pre><code>Dim str as String = "[1_5],[1_3],[1_5]"
  </code></pre>
  
  <p>The part before the _ can be variable is not a fix number 
  i need to convert it in to format </p>
  
  <pre><code>"5,3,5"
  </code></pre>
  
  <p>i have used the below code to obtain all the number that i need in the new string in the matches Item Groups</p>
  
  <pre><code>Dim pattern As String = "_(.*?)\]"
  Dim matches As MatchCollection = 
  Regex.Matches(rowpanel.getRequestedArea_selectionArea(), pattern, RegexOptions.Singleline)
  </code></pre>
  
  <p>My question is how i can join all the Groups to obtain the final string format ? </p>