title: Implementation of Expression.Assign in .Net 3.5 with same signature?
body: <p><code>Expression.Assign</code> isn't available before .NET 4. I need to implementation under .NET 3.5 of this method with original signature:</p>
  
  <pre><code>public static BinaryExpression Assign(
      Expression left,
      Expression right
  )
  </code></pre>
  
  <p>Clarification: I'm not looking for a way to use this method in the some case. I need to implement the general case.</p>