string.Join() in .net 3.5
<p>I have a .net 3.5 project in vs2008 and I'm trying to use <a href="http://msdn.microsoft.com/en-us/library/dd783876%28VS.90%29.aspx">this overload</a> of <code>string.Join()</code> (the one that takes a <code>string</code> and <code>IEnumerable&lt;T&gt;</code>) and the compiler does not seem to know about this overload.</p>

<p>This is the code that I tried</p>

<pre><code>    var result = string.Join(" ", Foo());
</code></pre>

<p>where <code>Foo()</code> is</p>

<pre><code>    IEnumerable&lt;string&gt; Foo()
    {

        foreach(string s in new []{"1", "2", "3"} )
        {
            yield return s;
        }
    }
</code></pre>

<p>I get</p>

<pre><code>&gt; Error 2   Argument '2': cannot convert from
&gt; 'System.Collections.Generic.IEnumerable&lt;string&gt;' to 'string[]'
</code></pre>

<p>Of course, if I use <code>Foo().ToArray()</code> it works but I'm wondering why the overload that takes <code>IEnumerable&lt;T&gt;</code> won't work.</p>

<p>MSDN in classic view says it's compatible with vs2008/.net 3.5</p>

<p><img src="http://i.stack.imgur.com/TLYDE.png" alt="enter image description here"></p>

<p>(I couldn't find the message "This page is specific to...." in non-classic views so I thought I'd put up a screen-cap.)</p>
