Memory Leak detection

Hi all,

I am new to c++. I have written one c++ application. I want to detect
memory leaks from  my program.

I tried with following code which i got from net.
	if(_CrtDumpMemoryLeaks() == TRUE)  // re****ts no leak

	{
		printf("detected 1");
	}
	 int *foo = new int[4];

    if(_CrtDumpMemoryLeaks() == TRUE)//re****ts a memory leak

	{
		printf("detected 2");
	}
     delete[] foo;
     foo = NULL;
   	if(_CrtDumpMemoryLeaks() == TRUE)// re****ts no leak

	{
		printf("detected 3");
	}



Ideally first time i should not get any memory leak.  But when i run
above code all print statements are executed.

Can anyone tell me why this is happening?

Please correct me if i am wrong.

thanks in advance.