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

I suspect that this pattern comes from translating C++ code to C# without pausing to understand the differences between C# finalization and C++ finalization. In C++ I often null things out in the destructor, either for debugging purposes (so that you can see in the debugger that the reference is no longer valid) or, rarely, because I want a smart object to be released. (If that's the meaning I'd rather call Release on it and make the meaning of the code crystal-clear to the maintainers.) As you note, this is pretty much senseless in C#.

You see this pattern in VB/VBScript all the time too, for different reasons. I mused a bit about what might cause that here:

http://blogs.msdn.com/b/ericlippert/archive/2004/04/28/122259.aspx