PRNG in C#, VB, result is different, can someone help me?

[BarkingFrog]

I'm only using this for personal use, just to calculate things..
but I need some help.. I use VisualStudio 2005

first, i used VB

Private Function PRNG(ByVal seed As String) As String
  Dim temp As String = ""
  Dim t As UInt64
  t = Convert.ToUInt64("0x41C64E6D", 16) * Convert.ToUInt64(seed, 16) + Convert.ToUInt64("0x6073", 16)
  temp = Hex(t)
  If temp.Length < 16 Then
    For t = 0 To 15 - temp.Length Step 1 'just to add zero
      temp = "0" & temp
    Next
  End If
  PRNG = temp
End Function

then for some reason i have to convert it to C#, here is the code:

using Microsoft.VisualBasic; //for Conversion

private const UInt64 factor = 0x41C64E6D;
private const UInt64 adder = 0x6073;

//...

private string generate(String seed) {
  return temp =  Conversion.Hex( (factor * Convert.ToUInt64(seed, 16) + adder));
}

but i get different result, well the LSB is the same, but the MSB is different.. any clue?

thx a lot

[codemonkey85]

I am not sure why the result would be different, but here's what the VB.Net code converted to C# looks like for me (courtesy of this page.):

private string PRNG(string seed)
{
    string temp = "";
    UInt64 t = default(UInt64);
    t = Convert.ToUInt64("0x41C64E6D", 16) * Convert.ToUInt64(seed, 16) + Convert.ToUInt64("0x6073", 16);
    temp = Conversion.Hex(t);
    if (temp.Length < 16) {
        for (t = 0; t <= 15 - temp.Length; t += 1) {
            //just to add zero
            temp = "0" + temp;
        }
    }
    return temp;
}

[mingot]

public UInt32 GetNext32BitNumber()
{
seed = seed * 0x41C64E6D + 0x6073;

return seed;
}

No need for all that 64 bit stuff.

[damio]

public UInt32 GetNext32BitNumber()
{
seed = seed * 0x41C64E6D + 0x6073;

return seed;
}

No need for all that 64 bit stuff.

Shouldn't it be seed = (seed * 0x41C64E6D + 0x6073) & 0xFFFFFFFF;
?

[mingot]

Nope. The return will be uint anyhow.

[BarkingFrog]

Thanks for all of the help, I'll try that again..
oh, for the UInt64, i've tried UInt32, sometimes it says overflow.. so I decided to use UInt64.. but I think Mingot is correct, I'll try again..

@Damio
the modulo thing is somehow does not effect the result..

well I think it's because the conversion, somehow the result from C# is like rounded up..

thanks all..