RadExpressionEditor's Expression property exposes a LambdaExpression. You could cast the value of the Expression property to LambdaExpression and call the Compile method of LambdaExpression, which returns a Delegate.
In regard to your question, you can use the RadExpressionEditor to build expressions within a WPF environment and then Compile() the returned LambdaExpression. Once you have the result method you could work with it.
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