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Asked: 2026-05-12T12:11:59+00:00

I fully appreciate the atomicity that the Threading.Interlocked class provides; I don’t understand, though,

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I fully appreciate the atomicity that the Threading.Interlocked class provides; I don’t understand, though, why the Add function only offers two overloads: one for Integers, another for Longs. Why not Doubles, or any other numeric type for that matter?

Clearly, the intended method for changing a Double is CompareExchange; I am GUESSING this is because modifying a Double is a more complex operation than modifying an Integer. Still it isn’t clear to me why, if CompareExchange and Add can both accept Integers, they can’t also both accept Doubles.

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  1. Editorial Team

    The Interlocked class wraps around the Windows API Interlocked** functions.

    These are, in turn, wrapping around the native processor API, using the LOCK instruction prefix for x86. It only supports prefixing the following instructions:

    BT, BTS, BTR, BTC, XCHG, XADD, ADD, OR, ADC, SBB, AND, SUB, XOR, NOT, NEG, INC, DEC

    You’ll note that these, in turn, pretty much map to the interlocked methods. Unfortunately, the ADD functions for non-integer types are not supported here. Add for 64bit longs is supported on 64bit platforms.

    Here’s a great article discussing lock semantics on the instruction level.

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