Are there any official ways to write an Immediately Invoked Function Expression?

Question

Something like this:

var myObject = new MyClass() {     x = " ".Select(y =>     {         //Do stuff..         if (2 + 2 == 5)             return "I like cookies";         else if (2 + 2 == 3)             return "I like muffins";         //More conditions...         else             return "I'm a bitter old man";     }) }; 

I realize Select is not intended to be used this way. But yeah, what are some other ways to do the same thing?

Answer 1

For real code make it a function... For entertainment purposes C# equivalent of JavaScript IIFE is more direct than Select:

var myObject = new MyClass() {    x =((Func<int>)(() => {return 2;}))(),... 

Answer 2

I'm surprised no one's mentioned this yet, but you could use the Lazy<T> class:

var myObject = new MyClass() {     x = new Lazy<string>(() =>     {         //Do stuff..         if (2 + 2 == 5)             return "I like cookies";         else if (2 + 2 == 3)             return "I like muffins";         //More conditions...         else             return "I'm a bitter old man";     }).Value // <-- Evaluate the function here }; 

Alternatively, if you want to avoid having to specify the return type anywhere (as you do with new Lazy<string> because constructors do not support type inference), you can implement a simple generic method like this:

public static T Eval<T>(Func<T> func) {     return func(); } 

And then you can call like this:

var myObject = new MyClass() {     x = Eval(() =>     {         //Do stuff..         if (2 + 2 == 5)             return "I like cookies";         else if (2 + 2 == 3)             return "I like muffins";         //More conditions...         else             return "I'm a bitter old man";     }) }; 

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Update: C#7 introduces local functions. These are not really IFFEs, but they may solve a variety of related issues. For example:

var myObject = new MyClass() {     x = GetX() };  string GetX() {     //Do stuff..     if (2 + 2 == 5)         return "I like cookies";     else if (2 + 2 == 3)         return "I like muffins";     //More conditions...     else         return "I'm a bitter old man"; } 

The key here is that GetX can be declared within the same method as myObject share the same scope as it.