Why does C# execute Math.Sqrt() more slowly than VB.NET?

Question

Background

While running benchmark tests this morning, my colleagues and I discovered some strange things concerning performance of C# code vs. VB.NET code.

Answer 1

I agree with the statement that the C# code is computing sqrt on every iteration and here is the proof straight out of Reflector:

VB version:

private static void testIfPrimeSerial(int suspectPrime)
{
    int VB$t_i4$L0 = (int) Math.Round(Math.Sqrt((double) suspectPrime));
    for (int i = 2; i <= VB$t_i4$L0; i++)
    {
        if ((suspectPrime % i) == 0)
        {
            return;
        }
    }
    temp.Add(suspectPrime);
}

C# version:

 private void testIfPrimeSerial(int suspectPrime)
{
    for (int i = 2; i <= Math.Sqrt((double) suspectPrime); i++)
    {
        if ((suspectPrime % i) == 0)
        {
            return;
        }
    }
    this.temp.Add(suspectPrime);
}

Which kinda points to VB generating code that performs better even if the developer is naive enough to have the call to sqrt in the loop definition.