Evaluate C# expression inside another expression

Question

I want to use an expression in another one:

Expression<Func<double, double>> f = x => x * x * 27 + blah ... expression with x;

Expression<Func<double, double>> g = y => 3 + 8 * f.Compile()(y) * y * blah... expression with y and f(y);

This will not work when sent to LINQ to SQL because f.Compile() is unknown to SQL.

How do you evaluate the expression f on the variable y without compiling it, but still using normal syntax to define g?

I don't want to have to define all of g with some unreadable Expression.Add/Expression.Multiply etc. statements.

Thanks.

Konstantin Oznobihin · Accepted Answer · 2011-08-08 05:56:49Z

3

Take a look at Calling functions in LINQ queries and LINQ Extensions project. CLinq part is irrelevant to your question, but it also includes LinqExt library, which is just what are you looking for. The same approach is also used by LinqKit which also provides other useful extensions for Linq.

edited Aug 8, 2011 at 5:56

answered Aug 8, 2011 at 5:50

Konstantin Oznobihin

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3 Comments

SemMike Over a year ago

Thanks a lot, I downloaded LinqKit from the link you gave and it works perfectly with Invoke and AsExpandable. I agree, very interesting articles.

Vladimir Over a year ago

Would have been good to show what syntax it works.

Konstantin Oznobihin Over a year ago

@Vladimir the thing is there was no such syntax in C# and you had to use 3rd party libraries with their own syntax or you could have implemented something on your own. Anyway it's a bit late to do anything regarding your comment, cause I haven't been using .NET for several years now.

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