Bitwise operation on longs

Question

I trying to compile this code:

Int64 itag = BitConverter.ToInt64(temp, 0);
itag &= 0xFFFFFFFFFFFFFC00;

However this gives me the following error:

Operator '&=' cannot be applied to operands of type 'long' and 'ulong'

How do I do this?

Answer 1

See http://msdn.microsoft.com/en-en/library/aa664674%28v=vs.71%29.aspx .

If the literal has no suffix, it has the first of these types in which its value can be represented: int, uint, long, ulong.

You have

0xFFFFFFFFFFFFFC00

but Int64.Max is:

0x7FFFFFFFFFFFFFFF

so long is not big enough and ulong is taken as the type of the literal.

Now you have on the left side a Int64, which is signed, and on the right side you have ulong, however, there is not overload of &= which accepts that combination, which leads to the error.

Answer 2

C# uses the smallest fitting type for integer literals and 0xFFFFFFFFFFFFFC00 is too big for long so it's an ulong.

So either convert itag to ulong or 0xFFFFFFFFFFFFFC00 to long (unchecked).