Use of return keyword in code block

Question

What is the difference between saying:

if (abc == "a")
{
// do something here...
return;
}

and the same as above, but without the return keyword?

I am a C# coder and I know that the return keyword followed by a type or variable returns that item, but in the above context, return seems to be just to exit the code block but does it make any functional or performance change on the code?

Thanks

Answer 1

"return" exits from the function, not just the enclosing code block. So if your code block was in the context of a function, like so (I don't know C# so I'm using Java syntax):

int thisIsAFunction(int a) {
    if (abc == "a")
    {
        // do something here...
        return 1;
    }
    // do something else here...
}

if abc == "a" then the "do something else here" will not run. But if you removed the return statement inside the if block, then it would run.

Answer 2

return statement exits the function immediately, so it might have performance benefits as the following code in the function would not be executed at all.

Answer 3

In your case, no - but if you had other code after your 'if' statement that you only wanted to run if your statement was false (e.g. if abc != "a"), then the return allows you to bypass that and exit the function / method.

Answer 4

Executing the return statement will make the execution jump out of the method. Without the return, it would simply go on with the next statement instead.

Answer 5

MSDN

The return statement terminates execution of the method in which it appears and returns control to the calling method. It can also return an optional value. If the method is a void type, the return statement can be omitted.

Example

//this would do nothing
public void method()
{
   return;
}


 //this would return true
 //notice the return type of bool this means
 //the method expects a true\false value
public bool method2()
{
   return true;
}

public void test()
{
    if(method2())
        method()
}

Now if you ran test method2 would always return true and method1 would just end its processing

Answer 6

Yes, your method does not have return type in this case. e.g.

public void Foo
{
 if (abc == "a")
 {
  // do something here...
  return;
 }
 // some other code
}

This is to say if abd = "a", then exit the method so that some other code won't be executed.

Answer 7

In a loop or case statement, you can use break to achieve this result. This doesn't work on if statements or code blocks in general though.

And yes, return exits the enclosing function.

Answer 8

The return statement does exit the current method, not just the code block (for/while/if/etc). So it is useful for situations like the following:

public void MyMethod(object myObject)
{
    if (myObject == null)
    {
        return;  // exits method.
    }

    // do something with myObject
}

Additional info: I will point out, that many people prefer to have one exit point in a method, however, it can be useful to do something similar to the example here in some cases. I would always try to find ways to limit the number of return or exit points in your method.

Answer 9

It can be a cleaner way of writing code. I typically do it in a guard clause at or near the beginning of a method. If you have an error condition, just "return" out of the method. It saves wrapping the rest of your work in an else block. Seems trivial, but it helps to reduce code complexity.