The documentation of T-SQL Rand() says:
Repetitive calls of RAND() with the same seed value return the same results.
This is really convenient, but what if you want to repeat the same series in C# or in any other language?
The code below allows you to do just that.
It took me quite a bit of time to get to this final version. I had to use various techniques to get it exactly right.
I love the 12345 and 67890 at the end.
When i got this bit, I knew it must be right.
public class SQLRand
private static int n1;
private static int n2;
#region "PRIVATE METHODS"
private static void ShiftAndCarry(ref int n, int LEQA, Int64 MULTIPLIER, int SHIFT, int MODULUS)
n = n * LEQA - ((int)(n * MULTIPLIER >> SHIFT)) * MODULUS;
if (n < 0) n += MODULUS;
private static int IntRand()
int result = n1 - n2;
if (result < 1) result += (2147483563 - 1); return result;
#endregion "PRIVATE METHODS"
public static double Rand()
const double RAND_DIVIDER = 2147483589.4672801884116202;
return IntRand() / RAND_DIVIDER;
public static double Rand(int seed)
n1 = (seed < 0 ? -seed : seed == 0 ? 12345 : seed);
n2 = 67890;
For info the algoritm uses, two of the bigger prime that would fit a C# integer.
The biggest prime number that would fit is int.MaxValue = 2^31 - 1 = 2,147,483,647 (the 105,097,565th prime)
I would quite like someone to go further and describe the algorithm.
It must be described somewhere