Calling a function inside of a lambda expression

Question

In C#, is it possible to call a function inside of a lambda expression?

For example, here are some contents of lambda expression:

(a => a.testBool && a.testBool2)

Is it possible to write the above contents into a function, and call the function inside of the lambda expression to get the same results?

Thanks in advance.

EDIT

In my original post, I did not state that this is for a dbSet.

I have created the following function in the test object (a) as follows:

public bool testBool()
{
    return true;
}

When calling the following code:

(a => a.testBool()).ToList()

I am getting this error:

LINQ to Entities does not recognize the method 'Boolean testBool()' method, and this method cannot be translated into a store expression.

ofcourse you can call a method from a lamda, lambdas are also methods.there is nothing special about them. so you can do anything you do in a normal method. — Selman Genç, Jan 29 '15 at 12:12
Have you tried to write the above contents into a function, and call the function inside of the lambda? — Dave Becker, Jan 29 '15 at 12:12
Are you using the lambda to create a delegate, or to create an expression tree? If you're trying to create a delegate, it's easy. If you're trying to create an expression tree, it's still possible, but a lot more complicated. — , Jan 29 '15 at 12:14

score 0 · Answer 1 · answered Jan 29 '15 at 12:12

0

Sure, if its a function declared in class a.

public class a
{
    bool testBool()
    {
     ...
    }

    bool testBool2()
    {
     ...
    }
}

Then you can do:

ListA.Where(a => a.testBool() && a.testBool2()).ToList();

answered Jan 29 '15 at 12:12

kassi

Sure this will work? With a `void` function? – musefan Jan 29 '15 at 12:13
You're right, corrected the answer ;) – kassi Jan 29 '15 at 12:15
That method needs to return a boolean; and it should be "Linq to objects". Don't try it with "Linq to SQL" – Sriram Sakthivel Jan 29 '15 at 12:15
are you confusing the projected instance of 'a' (in the lambda) with a class 'a'. in your example where are you instantiating a? – Dave Becker Jan 29 '15 at 12:15
1

@DaveBecker I'm assuming `ListA` is an instance of `List` that already contains items. That part of the answer looks okay to me. – Jan 29 '15 at 12:16
Im assuming nothing. The answer is no different to the OPs example except that testBool is now a function not a property. Not quite what they asked. – Dave Becker Jan 29 '15 at 12:17
Why -1? I've just given him an example how this could work. I just didn't want to answer with an simple "Yes!". :S – kassi Jan 29 '15 at 12:20
@kassi: Can you have a look at my edit please? – Simon Jan 30 '15 at 01:39

1 Answers1