Is there an inverse operation to Expression.Lambda?

Question

Is there an inverse operation to Expression.Lambda<...>(originalExpression, parameterExpression) that would return me the original expression?

Context:

I am creating a lambda expression using the lambda syntax (not using the Expression class at all) like this:

 return item => item.Something

In a different layer of the application, I would like to "un-lambda" this expression, apply

expression= Expression.Not(expression);

to it and then wrap it to a lambda again.

Is this possible?

score 4 · Accepted Answer · answered Dec 06 '13 at 12:27

4

LambdaExpression.Body is your original expression, so you can do

var inverted = Expression.Lambda(Expression.Not(lambda.Body), lambda.Parameters);

answered Dec 06 '13 at 12:27

Jon

Thank you! I was struggling with the parameters, I was passing a new ParameterExpression (same count and types of arguments) in the Lambda call and apparently I have to pass in the very same instance of parameters that the lambda was using. – Tomas Grosup Dec 06 '13 at 12:59
@TomasGrosup: [I had that problem myself](http://stackoverflow.com/q/2797261/50079) in the past ;-) – Jon Dec 06 '13 at 13:02

1 Answers1