Re: Structures not behaving as value types

Richard Kucia wrote:

<snip>

> Public Shared Operator <<(ByVal Operand As strFieldMask, ByVal Bits As Integer) As strFieldMask
> Dim Result As strFieldMask
> Dim BitCrossing As Integer
> ' Brute force method: shift one bit at a time
> Result = Operand

The last quoted line above is the guiltiest line in this particular case
- by copying the operand as the result, the reference is copied for the
array, so changes to the result (i.e. the shifting itself) also affect
the operand.

However, what you're seeing is primarily due to breaking another more
general rule: don't make structures mutable. It's very fragile, as
you've discovered - and the behaviour you've seen isn't the only
unexpected result you might encounter.

Embedding a reference type within a value type is *rarely* a good idea,
but it's not too bad if either the reference type itself is immutable,
or the reference will only ever be a private one and you only use it in
an immutable way.

Jon

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