Collection was modified; enumeration operation may not execute." Collection elements are not modified
<p>I have a nested loop "structure" in my code. Sometimes, I get the below message.</p>

<blockquote>
  <p>Collection was modified; enumeration operation may not execute.</p>
</blockquote>

<p>I have a collection I am looping through, like below. <code>Coll</code> is a <code>List&lt;string&gt;</code></p>

<pre><code>foreach (string[] s1 in obj.Coll
{
    foreach (string s in s1) { }
}
</code></pre>

<p>For each string in the array, I need to work with it (read as read the value, not write). 
All I do with it is get directories (this value is a path) and split this string into an array.</p>

<p>How can this be resolved?</p>
