Question

If I have a for loop which is nested within another, how can I efficiently come out of both loops (inner and outer) in the quickest possible way?

I don’t want to have to use a boolean and then have to say go to another method, but rather just to execute the first line of code after the outer loop.

What is a quick and nice way of going about this?

I was thinking that exceptions aren’t cheap/should only be thrown in a truly exceptional condition etc. Hence I don’t think this solution would be good from a performance perspective.

I don’t feel it it is right to take advantage of the newer features in .NET (anon methods) to do something which is pretty fundamental.

Answer 1

Well, goto, but that is ugly, and not always possible. You can also place the loops into a method (or an anon-method) and use return to exit back to the main code.

    // goto     for (int i = 0; i < 100; i++)     {         for (int j = 0; j < 100; j++)         {             goto Foo; // yeuck!         }     } Foo:     Console.WriteLine('Hi'); 

vs:

// anon-method Action work = delegate {     for (int x = 0; x < 100; x++)     {         for (int y = 0; y < 100; y++)         {             return; // exits anon-method         }     } }; work(); // execute anon-method Console.WriteLine('Hi'); 

---

Note that in C# 7 we should get ‘local functions’, which (syntax tbd etc) means it should work something like:

// local function (declared **inside** another method) void Work() {     for (int x = 0; x < 100; x++)     {         for (int y = 0; y < 100; y++)         {             return; // exits local function         }     } }; Work(); // execute local function Console.WriteLine('Hi');