Rounding with number formatting in C#

gistfile1.cs

// No number specifier
Console.WriteLine("a) {0}", numSingle);

// Round up, ignore any decimal points.
Console.WriteLine("a) {0:##}", numSingle);

// Round up to 1 dp.
Console.WriteLine("b) {0:.#}", numSingle);

// Round up to 2 dp.
Console.WriteLine("c) {0:.##}", numSingle);

// Round up to 3 dp.
Console.WriteLine("d) {0:.###}", numSingle);

// Floats work up to 7 digits, then any extra digit after the decimal place is rounded up, or ignored.
// So 4 decimal places is the maximum a number up to 1000 can store, e.g. 999.1234.
// It's recommended to always use double (Double) or decimal (Decimal) for applications involving currencies.
double numDouble = 1000000.5664;
float numSingle2 = 999.9999f;
Console.WriteLine("e) {0:.####}", numDouble);
Console.WriteLine("e2) {0:.####}", numSingle2);
Console.WriteLine("e3) {0:##}", numSingle2);

Output:
a) 10.566
a) 11
b) 10.6
c) 10.57
d) 10.566
e) 1000000.5664
e2) 999.9999
e3) 1000