cvCreateButton VS2010 - visual-studio-2010

When I use the code
cvCreateButton("button1",callbackButton2,NULL,CV_PUSH_BUTTON,1);
void callbackButton2(int state, void *pointer){
int i = 2;
return;
}
I get the following error in visual studios 2010
error C2065: 'callbackButton2' : undeclared identifier
Could someone please explain what I am doing wrong to cause this error
Thanks

Based on the code presented it appears that callbackButton2 is used on the first line but is declared after this on the second line.
In most languages this is not a legal thing to do because an identifier is not valid until the compiler can determine the context(s) in which it can be used which is what declaring an identifier does
Try this:
void callbackButton2(int state, void *pointer){
int i = 2;
return;
}
cvCreateButton("button1",callbackButton2,NULL,CV_PUSH_BUTTON,1);
In that code sample the identifier callbackButton2is declared as a function before being used as an argument to the cvCreateButton function and should therefore be a valid use of the identifier

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C++ error C2065: 'Value' : undeclared identifier -Newbe

Hi I am new to Visual Studio 2010
When I try build my code it tells me:
count.cpp(18): error C2065: 'Value' : undeclared identifier
That is my count.cpp code giving out the error:
#include "StdAfx.h"
#include "count.h"
count::count(void): Value(0), ResetValue(0){} //constructor
count::~count(void){} //destructor
int GetValue(){return Value;} //Accessor to get value by another class
Here is my count.h code:
#pragma once
class count
{
public:
count(void);
virtual ~count(void);
int GetValue();
private:
int Value;
int ResetValue;
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It's a count object that's going to be used by a countWindow object.
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Is the variable Value not declared and initiated on the line 12 when I actually make use of the constructor?
Or is it not link to the declaration in the count.h file?
Because if I create another void function to just do a Value++, Visual studio seems fine with.
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