What does the tilde do in C#?

Question

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What does the tilde before a function name mean in C#?
What is the tilde (~) in the enum definition?

I know "~" is for Finalzier methods but now I saw some C# code like this:

if (~IsFieldDeleted(oRptField.GetLayoutField()) != 0)
{
   oCollection.Add(oRptField, oRptField.ObjectKeyString);
   // some more stuff
}

notice that "~" in the first line?

and then if I go to implementation of IsFieldDeleted it is a method that returns an int.

private int IsFieldDeleted(LayoutLib.LayoutField oLayoutField)
{
    Collection oColl = GetFieldIdsForField(oLayoutField);

    return (oColl.Count == 0) ? 1 : 0;

}

You could have googled this quite easily; http://msdn.microsoft.com/en-us/library/d2bd4x66%28v=vs.80%29.aspx — RJ Lohan, Dec 12 '12 at 20:49
If it's bitwise negation, then neither `~0` nor `~1` is zero. — John Dvorak, Dec 12 '12 at 20:49
i think it's bitwise negation. kinda like `!` except for each bit in a value. — Sam I am says Reinstate Monica, Dec 12 '12 at 20:50

score 2 · Answer 1 · edited Nov 30 '18 at 21:17

2

The ~ operator performs a bitwise complement.

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/bitwise-complement-operator

IsFieldDeleted() returns an int, which is a type to which that operator can be applied (int, uint, long, ulong). The bitwise complement is taken and then compared to zero.

I don't see how the if(...) can ever be true, since IsFieldDeleted() only returns 0 or 1 and ~0 and ~1 are both not zero.

edited Nov 30 '18 at 21:17

Lauren Rutledge

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answered Dec 12 '12 at 20:49

Eric J.

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`IsFieldDeleted` returns either `0` or `1`. Their complement is never zero. Perhaps this is a bug in the original code? – John Dvorak Dec 12 '12 at 20:52
@JanDvorak: Funny I was updating my post as you typed the comment. Agree 100%. – Eric J. Dec 12 '12 at 20:52
@EricJ. : Thanks for inmfo but when I put a break point inside the commands of that if(...) block it hits the break point. – Dec 12 '12 at 20:55
@user1899082: Try assigning the return value of `IsFieldDeleted()` to an int variable and share what that value is. – Eric J. Dec 12 '12 at 21:43
@EricJ. IsFieldDeleted was zero so its negate was negative one so it went inside the if block . – Dec 12 '12 at 21:52

What does the tilde do in C#?

1 Answers1