title: Convert 'System.Collections.Generic.IEnumerable<string>' to 'string[]
body: <p>I'm having issues with converting a piece of code to work with .NET3.5. </p>
  
  <pre><code>static Dictionary&lt;string, object&gt; dictionary = new Dictionary&lt;string, object&gt; 
  {
      {"key","value"},
      {"key2","value2"},
  };
  
  public static string Process(String _string)
  {
      var levels = new Dictionary&lt;string, object&gt;
      {
          { "", "" },
          { "-", "Light" },
          { "+", "Heavy" }
      };
      var search = string.Join("and ", from l in levels.Keys
                                 from w in dictionary.Keys
                                 join m in _string.Split() on string.Concat(l, w) equals m
                                 select string.Concat(levels[l], dictionary[w]));
  
      return search;
  }
  </code></pre>
  
  <p>I'm getting two errors when I try to compile...</p>
  
  <blockquote>
    <p>Argument 2: cannot convert from
    'System.Collections.Generic.IEnumerable' to 'string[]'</p>
  </blockquote>
  
  <p>and</p>
  
  <blockquote>
    <p>The best overloaded method match for 'string.Join(string, string[])'
    has some invalid arguments</p>
  </blockquote>
  
  <p>I thought about adding .ToArray(), but I didn't know where.</p>