每次按下键都会在文本框 VB.NET 中自动显示小数位答案

【问题标题】：EveryTime key is pressed will automatic decimal places in textbox VB.NET每次按下键都会在文本框 VB.NET 中自动显示小数位
【发布时间】：2021-01-26 09:57:23
【问题描述】：

我在文本框中使用了按键事件。当我按下“2”时，我的预期值应该是 0.02。但是它显示“20.02”

我尝试将文本框属性“RighttoLeft”设置为yes，以便在键入时从右侧开始。但我希望我键入的 keychar 不会附加到我在代码中使用的 FactorDecimal 的输出中。

请看下面的代码。我基于其他帖子的@Visual Vincent 评论：

 Private Sub txtChequeAmt_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtChequeAmt.KeyPress
    If Char.IsDigit(e.KeyChar) = False Then
        e.Handled = True
    End If

    FactorDecimal1.AppendNumber(e.KeyChar)
    txtChequeAmt.Text = FactorDecimal1.ToString()

End Sub

    Public Class FactorDecimal
    Private value As String = "0"

    Public DecimalPlaces As Integer

    Public Sub AppendNumber(Character As Char)
        If Char.IsNumber(Character) = False Then
            Throw New ArgumentException("Input must be a valid numerical Character!", "Character")
            value = (value & Character).TrimStart("0"c)
        Else
            value = (value & Character).TrimStart("0"c)
        End If
    End Sub

    Public Sub RemoveRange(Index As Integer, Length As Integer)
        If value.Length >= Me.DecimalPlaces + 1 AndAlso Index + Length > value.Length - Me.DecimalPlaces Then
            Length -= 1 'Exclude decimal point
        End If

        If Index + Length >= value.Length Then
            Length = value.Length - Index 'Out of range
            value = value.Remove(Index, Length)
        End If

        If value.Length = 0 Then
            value = "0"
        End If
    End Sub

    Public Overrides Function ToString() As String
        Dim Result As Decimal

        If (Decimal.TryParse(value, Result)) = True Then
            Return (Result / (10 ^ Me.DecimalPlaces)).ToString("0." & New String("0"c, Me.DecimalPlaces))

        End If

        Return (Result / (10 ^ Me.DecimalPlaces)).ToString("0." & New String("0"c, Me.DecimalPlaces))
    End Function

    Public Sub New(DecimalPlaces As Integer)
        If DecimalPlaces <= 0 Then
            DecimalPlaces = 1
        End If
        Me.DecimalPlaces = DecimalPlaces
    End Sub
End Class

【问题讨论】：

标签： vb.net textbox keypress

【解决方案1】：

如果你想在文本框中使用你的计算，你需要设置 e.Handled = True。

Private Sub txtChequeAmt_KeyPress(sender As Object, e As KeyPressEventArgs) 
    If Char.IsDigit(e.KeyChar) = False Then
        e.Handled = True
        ' No point to continue if it is not a digit because 
        ' in that case you throw into the AppendNumber. Better avoid the exception
        Return
    End If

    FactorDecimal1.AppendNumber(e.KeyChar)
    txtChequeAmt.Text = FactorDecimal1.ToString()

    ' Don't let the forms engine add the number to your textbox 
    ' you have already defined its content 
    e.Handled = True
End Sub

【讨论】：