.net – 百分比的NumericUpDown控件？

如何设置NumericUpDown控件以百分比形式显示值？ 您必须派生自己的自定义控件并覆盖UpdateEditText()方法.在我们处理它时,让我们覆盖默认的Minimum,Maximum和Increment属性值,使其更加符合百分比.

我们还需要覆盖基础ParseEditText()方法,将用户生成的输入解释为百分比(除以100),因为用户希望输入80代表80％(并且Decimal解析器需要忽略百分号).

Public Class PercentUpDown
    Inherits NumericUpDown

    Private Shared ReadOnly DefaultValue As New [Decimal](0.0)      ' 0%
    Private Shared ReadOnly DefaultMinimum As New [Decimal](0.0)    ' 0%
    Private Shared ReadOnly DefaultMaximum As New [Decimal](1.0)    ' 100%
    Private Shared ReadOnly DefaultIncrement As New [Decimal](0.01) ' 1%

    Public Sub New()
        Value = DefaultValue
        Minimum = DefaultMinimum
        Maximum = DefaultMaximum
        Increment = DefaultIncrement
    End Sub

    Protected Overrides Sub UpdateEditText()
        If UserEdit Then
            ParseEditText()
        End If

        Text = Value.ToString(String.Format("p{0}", DecimalPlaces))
    End Sub

    Protected Shadows Sub ParseEditText()
        Debug.Assert(UserEdit = True, "ParseEditText() - UserEdit == false")

        Try
            If Not String.IsNullOrWhiteSpace(Text) AndAlso _
               Not (Text.Length = 1 AndAlso Text.Equals("-")) Then

                Value = Constrain(Decimal.Parse(Text.Replace("%", String.Empty), NumberStyles.Any, CultureInfo.CurrentCulture) / 100)

            End If
        Catch ex As Exception
            ' Leave value as it is
        Finally
            UserEdit = False
        End Try
    End Sub

    Private Function Constrain(origValue As [Decimal]) As [Decimal]
        Debug.Assert(Minimum <= Maximum, "minimum > maximum")

        If origValue < Minimum Then Return Minimum
        If origValue > Maximum Then Return Maximum

        Return origValue
    End Function

End Class

我们可以通过添加TextFormat属性来扩展类的范围,我们可以在设计时设置我们想要使用的numeric display format,以便我们可以支持将值显示为货币.

但是,上面的代码非常简洁,特别是针对百分比,利用了现有的DecimalPlaces属性. Value属性存储为百分比的数学表示(例如,50为50％),因此插入公式很简单,而不必担心除以100.