title: SSIS Expression task can't see variables populated by a containing foreach loop
body: <p>I'm trying to collect a list of file paths from a directory, concatenate them together and then send that value to an execute process task. To do this, I'm using a ForEach loop with an expression task inside that is supposed to stuff the path from each iteration of the loop into a variable. The problem is that when the expression task runs it throws the following error. </p>
  
  <pre><code>Error: The type of the value (Empty) being assigned to variable "User::CombinedPath"
  differs from the current variable type (String). Variables may not change type
  during execution. Variable types are strict, except for variables of type Object.
  </code></pre>
  
  <p>The expression task is basically doing this:</p>
  
  <pre><code>@[User::PathFromForEach] + ";"
  </code></pre>
  
  <p>However, it appears that @[User::PathFromForEach] is coming in empty.</p>
  
  <p>What's going on here?</p>