What is the best way to combine two uints into a ulong in c#

Question

What is the best way to combine two uints into a ulong in c#, setting the high/low uints.

I know bitshifting can do it, but I don't know the syntax, or there maybe other APIs to help like BitConverter, but I don't see a method that does what I want.

Answer 1

ulong output = (ulong)highUInt << 32 + lowUInt

The << and >> operators bitshift to the left (higher) and right (lower), respectively. highUInt << 32 is functionally the same as highUInt * Math.Pow(2, 32), but may be faster and is (IMO) simpler syntax.

Answer 2

You have to convert the highInt to a ulong before you bitshift:

ulong output = highInt;
output = output << 32;
output += lowInt;

Answer 3

Encoding:

ulong mixed = (ulong)hi << 32 | lo;

Decoding:

uint lo = (uint)(mixed & uint.MaxValue);
uint hi = (uint)(mixed >> 32);