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c#funclinq-expressions

Extracting Func<> from Expression<>

I wanna extract the Func<> from the following Expression :

Expression<Func<IQueryable<Entity>, IOrderedQueryable<Entity>>> order = q => q.OrderByDescending(c=>c.FullName);

Func<IQueryable<Entity>, IOrderedQueryable<Entity>> orderFunc = ?

How can I do it?

Edit :

And how can we convert Func<IQueryable<Entity>, IOrderedQueryable<Entity>> to Expression<Func<IQueryable<Entity>, IOrderedQueryable<Entity>>> ?

Solution

  • You can use the Compile method to turn any Expresstion<TDelegate> into a TDelegate.

    There is no way to convert a delegate into an Expression<TDelegate>. The detailed information about what makes up the expression was lost when it was compiled into a delegate.

    You could, in theory create an expression who's body does nothing but invoke the given delegate, by doing something like this:

    Func<int> function = () => 42;
Expression<Func<int>> expression = () => function();

    but such an expression isn't really useful. There really isn't any meaningful information inside of that expression. So while it's technically possible, it's never really practical.