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    <h2>Note: This answer is old now. Iterator blocks have since been added to <a href="http://en.wikipedia.org/wiki/Visual_Basic_.NET" rel="nofollow noreferrer">VB.NET</a></h2> <p>C# translates the yield keyword into a state machine at compile time. VB.NET does not have the yield keyword, but it does have its own mechanism for safely embedding state within a function that is not easily available in C#.</p> <p>The C# <code>static</code> keyword is normally translated to Visual Basic using the <code>Shared</code> keyword, but there are two places where things get confusing. One is that a C# static class is really a Module in Visual Basic rather than a Shared class (you'd think they'd let you code it either way in Visual Basic, but noooo). The other is that VB.NET does have its own <code>Static</code> keyword. However, <code>Static</code> has a different meaning in VB.NET.</p> <p>You use the <code>Static</code> keyword in VB.NET to declare a variable inside a function, and when you do the variable retains its state across function calls. This is different than just declaring a private static class member in C#, because a static function member in VB.NET is guaranteed to also be thread-safe, in that the compiler translates it to use the Monitor class at compile time.</p> <p>So why write all this here? Well, it should be possible to build a re-usable generic <code>Iterator&lt;T&gt;</code> class (or <code>Iterator(Of T)</code> in VB.NET). In this class you would implement the state machine used by C#, with <code>Yield()</code> and <code>Break()</code> methods that correspond to the C# keywords. Then you could use a static instance (in the VB.NET sense) in a function so that it can ultimately do pretty much the same job as C#'s <code>yield</code> in about the same amount of code (discarding the class implemenation itself, since it would be infinitely re-usable).</p> <p>I haven't cared enough about Yield to attempt it myself, but it <em>should</em> be doable. That said, it's also far from trivial, as C# team member Eric Lippert calls this "<a href="http://blogs.msdn.com/ericlippert/archive/2009/08/24/iterator-blocks-part-seven-why-no-anonymous-iterators.aspx" rel="nofollow noreferrer">the most complicated transformation in the compiler</a>." </p> <p>I have also come to believe since I wrote the first draft of this over a year ago that it's not really possible in a meaningful way until Visual Studio 2010 comes out, as it would require sending multiple lambdas to the Iterator class and so to be really practical we need <a href="http://en.wikipedia.org/wiki/.NET_Framework" rel="nofollow noreferrer">.NET 4</a>'s support for multi-line lambdas.</p>
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