Math.Round

In .NET, the Math.Round function provides built-in logic. With the MidpointRounding enum we round with special options—away from zero, or to even.

Numbers can be rounded in many ways. The Math.Round function has forms that act on many numeric types, including Double and Decimal.

Rounding output

Consider the Double 1.234. When we call the Math.Round function on it, we receive the number 1—the fractional part was rounded down.

1.234 -> 1

Example

This program calls Math.Round on the Double 123.45. To call Math.Round With no options, we use just one argument. This rounds the number to 123.

Module Module1
    Sub Main()
        ' Call Math.Round on this Double.
        Dim before As Double = 123.45
        Dim after1 As Double = Math.Round(before, 1, MidpointRounding.AwayFromZero)
        Dim after2 As Double = Math.Round(before, 1, MidpointRounding.ToEven)
        Dim after3 As Double = Math.Round(before)

        Console.WriteLine(before)
        Console.WriteLine(after1)
        Console.WriteLine(after2)
        Console.WriteLine(after3)
        Console.WriteLine()

        ' Use on this Decimal.
        Dim before2 As Decimal = 125.101
        Dim after4 As Decimal = Math.Round(before2)
        Dim after5 As Decimal = Math.Round(before2, 1)

        Console.WriteLine(before2)
        Console.WriteLine(after4)
        Console.WriteLine(after5)
    End Sub
End Module
123.45
123.5
123.4
123

125.101
125
125.1

Notes, program

We also use Math.Round on the Decimal type. These have the same results as the Double type. The Math Class supports many numeric types, including Double and Decimal and others.

Rounding functionality is available in .NET. It is not needed to develop custom Functions in most programs. We instead invoke the Math.Round Shared Function, with 1 to 3 arguments.