VB.Net VS 2008验证textbox.text仅保留一个小数点

Question

Repected Sir, I am restricting my textbox for numbers and decimal points only, i am able to get numbers and decimals only by the below function but not able to restrict making decimal points appearing twice on the input textbox. I guess If singleChars.IndexOf(KeyChar) > 0 And (Asc(KeyChar)) <> 8 has some errors and if its wrong how to solve it ?

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        e.Handled = myClasses.onlyCurrency(e.KeyChar)
    End Sub

And my public function from class file is

Public Shared Function onlyCurrency(ByVal KeyChar As Char) As Boolean
        Dim allowedChars As String
        allowedChars = "0123456789."
        Dim singleChars As String
        singleChars = "."
        If allowedChars.IndexOf(KeyChar) = -1 And (Asc(KeyChar)) <> 8 Then
            Return True
        End If
        If singleChars.IndexOf(KeyChar) > 0 And (Asc(KeyChar)) <> 8 Then
            Return True
        End If
        Return False
    End Function

Yours faithfully Murulimadhav

Answer 1

You are not paying attention to what has already been entered in your TextBox, therefore your function has no idea how many decimals points have been entered. You need to either pass the TextBox's Text into your function or prescreen it before sending to your function. Something like this:

Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TextBox1.KeyPress
    e.Handled = myClasses.onlyCurrency(e.KeyChar, CType(sender, TextBox).Text)

End Sub



Public Shared Function onlyCurrency(ByVal KeyChar As Char, CurrentText As String) As Boolean
    Dim allowedChars As String
    allowedChars = "0123456789."
    Dim singleChars As String
    singleChars = "."
    If KeyChar = singleChars Then
        If CurrentText.Contains(singleChars) Then
            Return True
        End If
    End If
    If allowedChars.IndexOf(KeyChar) = -1 And (Asc(KeyChar)) <> 8 Then
        Return True
    End If
    Return False
End Function

Answer 2

Try Like this

Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As 
System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress

    If Char.IsDigit(e.KeyChar) = False AndAlso e.KeyChar <> "." Then
        e.Handled = True
    ElseIf e.KeyChar = "." AndAlso TextBox1.Text.Trim.Contains(".") Then
        e.Handled = True
    Else
        e.Handled = False
    End If

End Sub