Can Erten created a very useful expression tree to CodeDom converter. He wrote about it here: Expression Trees-Lambdas to CodeDom Conversion. I created a visual studio debugger visualizer based on it. You can find it in attachment. Just copy the assembly to My Documents\Visual Studio 2008\Visualizers and you're set. I also attached the full source code.

ExpressionCodeDomVisualizer.dll ExpressionCodeDomVisualizerSourceCode.zip