double someValue = 2.346;
string displayString = someValue.ToString("0.00");
Note that double.ToString (and therefore string.Format()) uses midpoint rounding away from zero, so 0.125 becomes 0.13. This is usually the desired behavior for display. These strings should obviously not be used for round-tripping.
This method is also inappropriate for rounding that is required in mathematical calculations (where MidpointRounding.ToEven is usually the best approach). In that case, Math.Round() should be used.
