How to Exit a Method without Exiting the Program?

Question

I am still pretty new to C# and am having a difficult time getting used to it compared to C/CPP.

How do you exit a function on C# without exiting the program like this function would?

if (textBox1.Text == "" || textBox1.Text == String.Empty || textBox1.TextLength == 0)
    textBox3.Text += "[-] Listbox is Empty!!!!\r\n";
System.Environment.Exit(0);

This will not allow return types and if left alone it will keep going on through the function unstopped. Which is undesirable.

@John I've been programming in C# and other OOP languages for a good time now and I still call them functions. (and I'm only 19!) — Earlz, Jul 22 '10 at 23:40
@Earlz: maybe it's just me, but I find that most people who still say "function", or "subroutine" don't know OO. Therefore, hearing someone say "function" gives me the impression they don't know OO. — John Saunders, Jul 22 '10 at 23:43
Every method is a function, and is also a subroutine (but not every function or subroutine is a method). In any case, in my favorite language it's called "member functions", and that's the way I likes them! ;) — Pavel Minaev, Jul 22 '10 at 23:54
@John, a method, to me, implies operating on an instance. A function operates on its arguments, regardless of whether or not it is static. A method is a sub-case of functions that operate on an instance, where there the instance is the first argument (implied or explicit, depending on your language). — Nathan Ernst, Jul 22 '10 at 23:59
@Nathan: I prefer "instance method" and "static method" or "class method". Functions are a non-OO concept, and don't refer to the concept of a class. — John Saunders, Jul 23 '10 at 00:43
To most the difference between "method" and "function" is like the difference between "armor" and "armour" or "color" and "colour". It depends on how you look at it. — ThrowingDwarf, Jun 17 '16 at 09:36
Methods can be distinguished from functions with the rule that they require the runtime type of an argument or arguments (multi-methods) to determine how dispatch them. One could also say a method is encapsulated by a class or object, which would accommodate static methods and javascript prototypes, but might exclude multi-methods. The first would allow "function" to be used for "statically dispatched" execution bits; the second would only allow for "bare" execution bits (not possible in Java, but certainly so in c# and javascript, c++ and c). — Gerard ONeill, Jul 24 '23 at 18:29

score 168 · Accepted Answer · edited May 23 '17 at 12:18

There are two ways to exit a method early (without quitting the program):

Use the return keyword.
Throw an exception.

Exceptions should only be used for exceptional circumstances - when the method cannot continue and it cannot return a reasonable value that would make sense to the caller. Usually though you should just return when you are done.

If your method returns void then you can write return without a value:

return;

Specifically about your code:

There is no need to write the same test three times. All those conditions are equivalent.

You should also use curly braces when you write an if statement so that it is clear which statements are inside the body of the if statement:

if (textBox1.Text == String.Empty)
{
    textBox3.Text += "[-] Listbox is Empty!!!!\r\n";
}
return; // Are you sure you want the return to be here??

If you are using .NET 4 there is a useful method that depending on your requirements you might want to consider using here: String.IsNullOrWhitespace.
You might want to use Environment.Newline instead of "\r\n".
You might want to consider another way to display invalid input other than writing messages to a text box.

It was so simple! Just return without a value! Thanks a lot! I was returning with 0. =) — Nightforce2, Jul 22 '10 at 23:31
Or `string.IsNullOrEmpty` (pre .Net 4 shout-out - which, of course does not detect whitespace-only strings). Sadly, not all of us can use 4.0, yet. — Nathan Ernst, Jul 23 '10 at 00:03
"return" doesn't work if you're in a nested piece of code, such as in a "catch". — as9876, Jul 03 '17 at 18:17

score 9 · Answer 2 · answered Jul 22 '10 at 23:31

In addition to Mark's answer, you also need to be aware of scope, which (as in C/C++) is specified using braces. So:

if (textBox1.Text == "" || textBox1.Text == String.Empty || textBox1.TextLength == 0)
    textBox3.Text += "[-] Listbox is Empty!!!!\r\n";
return;

will always return at that point. However:

if (textBox1.Text == "" || textBox1.Text == String.Empty || textBox1.TextLength == 0)
{
    textBox3.Text += "[-] Listbox is Empty!!!!\r\n";
    return;
}

will only return if it goes into that if statement.

score 3 · Answer 3 · answered Aug 06 '13 at 14:45

3

I would use return null; to indicate that there is no data to be returned

answered Aug 06 '13 at 14:45

beaumondo

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score 1 · Answer 4 · edited Apr 10 '18 at 17:53

1

The basic problem here is that you are mistaking System.Environment.Exit for return.

edited Apr 10 '18 at 17:53

Maxime

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answered Jul 23 '10 at 00:13

Loren Pechtel

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score 0 · Answer 5 · edited Jul 14 '22 at 10:10

0

If the function is a void, ending the function will return. Otherwise, you need to do an explicit return someValue. As Mark mentioned, you can also throw an exception.

edited Jul 14 '22 at 10:10

Dharman

30,962
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answered Jul 22 '10 at 23:28

Throwing an exception in this case is not best practice – pungggi Feb 10 '15 at 14:16

score 0 · Answer 6 · answered Jul 23 '10 at 03:56

@John, Earlz and Nathan. The way I learned it at uni is: functions return values, methods don't. In some languages the syntax is/was actually different. Example (no specific language):

Method SetY(int y) ...
Function CalculateY(int x) As Integer ...

Most languages now use the same syntax for both versions, using void as a return type to say there actually isn't a return type. I assume it's because the syntax is more consistent and easier to change from method to function, and vice versa.

How to Exit a Method without Exiting the Program?

6 Answers6

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