How to shift all the whole numbers in a double to the right of the point

This sounds like a pretty bizarre task, to be honest, but you could use:

while (Math.Abs(value) >= 1)
{
    value = value / 10;
}

That will go into an infinite loop if the input is infinity though - and you may well lose information as you keep dividing. The latter point is important - if what you're really interested in is the decimal representation, you should consider using decimal instead of double.

You could potentially use a mixture of Math.Log and Math.Pow to do it, but the above is probably what I'd start with.