Where did variable = null as “object destroying” come from?

Question

Working on a number of legacy systems written in various versions of .NET, across many different companies, I keep finding examples of the following pattern:

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Answer 1

It comes from C/C++ where doing a free()/delete on an already released pointer could result in a crash while releasing a NULL-pointer simply did nothing.

This means that this construct (C++) will cause problems

void foo()
{
  myclass *mc = new myclass(); // lets assume you really need new here
  if (foo == bar)
  {
    delete mc;
  }
  delete mc;
}

while this will work

void foo()
{
  myclass *mc = new myclass(); // lets assume you really need new here
  if (foo == bar)
  {
    delete mc;
    mc = NULL;
  }
  delete mc;
}

Conclusion: IT's totally unneccessary in C#, Java and just about any other garbage-collecting language.