小数点以下の数値を丸める方法は、場合により異なるため関数を作成する必要があります。

例えば、切り捨て１．５なら１にして－１．５なら－１にする関数は標準ではありません。

小数点以下を切り捨てする

Public Shared Overloads Function RoundDown(ByVal val As Double) As Double
    If 0.0 < val Then
        return Math.Floor(val)
    Else
        return Math.Ceiling(val)
    End If
End Function

Public Shared Overloads Function RoundDown(ByVal val As Decimal) As Decimal
    If 0.0 < val Then
        return Math.Floor(val)
    Else
        return Math.Ceiling(val)
    End If
End Function

 

小数点以下を切り上する

Public Shared Overloads Function RoundUp(ByVal val As Double) As Double
    If 0.0 < val Then
        return Math.Ceiling(val)
    Else
        return Math.Floor(val)
    End If
End Function

Public Shared Overloads Function RoundUp(ByVal val As Decimal) As Decimal
    If 0.0 < val Then
        return Math.Ceiling(val)
    Else
        return Math.Floor(val)
    End If
End Function

 

小数点以下を四捨五入する

Public Shared Overloads Function SimpleRound(ByVal val As Double) As Double
    Return Math.Round(val, MidpointRounding.AwayFromZero)
End Function

Public Shared Overloads Function SimpleRound(ByVal val As Decimal) As Decimal
    Return Math.Round(val, MidpointRounding.AwayFromZero)
End Function

 

少数桁を指定しての丸め処理

'少数桁を指定して小数点以下を切り捨て
Public Shared Overloads Function RoundDown(ByVal val As Double, digit As short) As Double
    Dim d As double = Math.Pow(10.0, digit)
    return ((RoundDown(val * d) / d))
End Function

'少数桁を指定して小数点以下を切り上
Public Shared Overloads Function RoundUp(ByVal val As Double, digit As short) As Double
    Dim d As double = Math.Pow(10.0, digit)
    return ((RoundUp(val * d) / d))
End Function

'少数桁を指定して小数点以下を四捨五入
Public Shared Overloads Function SimpleRound(ByVal val As Double, digit As short) As Double
    Dim d As double = Math.Pow(10.0, digit)
    return ((SimpleRound(val * d) / d))
End Function