Ref int question in C#

Question

Simply put, I am using a while loop to repeat a method, and each time the method is run the int "i" will increase by 1. Although I am having trouble calling the "NumberUp" method. error output is below.

Main method:

while (true)
{
    NumberUp(0);
}

NumberUp Method:

public static void NumberUp(ref int i)
{
    i++;
    System.Console.WriteLine(i);
}

I keep getting the following error:

The best overloaded method match for 'ConsoleApplication2.Program.NumberUp(ref int)' has some invalid arguments

Are you trying to increment the value of the literal `0`? It doesn't maker sense to pass a literal as a `ref`. — SLaks, Aug 10 '11 at 13:55
Possible duplicate of [Why use the 'ref' keyword when passing an object?](http://stackoverflow.com/questions/186891/why-use-the-ref-keyword-when-passing-an-object) — Jim Fell, May 27 '16 at 17:08

score 21 · Accepted Answer · answered Aug 10 '11 at 13:55

21

To call a method that takes a ref parameter, you need to pass a variable, and use the ref keyword:

int x = 0;
NumberUp(ref x);
//x is now 1

This passes a reference to the x variable, allowing the NumberUp method to put a new value into the variable.

answered Aug 10 '11 at 13:55

SLaks

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score 2 · Answer 2 · answered Aug 10 '11 at 13:55

2

Ref is used to pass a variable as a reference. But you are not passing a variable, you are passing a value.

 int number = 0;
 while (true)
 {
      NumberUp(ref number );
 }

Should do the trick.

answered Aug 10 '11 at 13:55

dowhilefor

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score 1 · Answer 3 · answered Aug 10 '11 at 13:55

1

A ref parameter needs to be passed by ref and needs a variable:

int i = 0;
while (true)
{
    NumberUp(ref i);
}

answered Aug 10 '11 at 13:55

Daniel Hilgarth

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1

Now that would be daft! Declare `i` outside the loop! – leppie Aug 10 '11 at 13:56

score 1 · Answer 4 · answered Aug 10 '11 at 13:55

1

You have to pass 0 as a reference in a variable containing 0, for instance:

int i = 0;
NumberUp(ref i);

Read here at MSDN for more information on the ref keyword.

answered Aug 10 '11 at 13:55

That's poorly phrased. You need to pass a reference to a variable containing `0`. – SLaks Aug 10 '11 at 14:00

score -1 · Answer 5 · edited Aug 10 '11 at 14:15

-1

ref

NumberUp(ref number );

edited Aug 10 '11 at 14:15

CharithJ

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answered Aug 10 '11 at 14:13

ABCD

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Ref int question in C#

5 Answers5