VB Text Box accepting Non numeric Data - vb.net

Question

I have a text box in VB which is set up to only accept only numeric data, and it works, except in TWO specific cases.
If the user provides a NON NUMERIC CHAR the text box self clears,
However, if the user first provides a number, then provides either '-' or '+'
The text box will accept this as a valid input.
When the user types one more char of ANY TYPE, i.e. number or char
Then the text box 'realises' and will self clear.
I was wondering if this is due to the way VB stores the chars '-' and '+'?
Is the best way around this to just add in the two exceptions, i.e. if '-' or '+' are input then self clear?
Or is there a more elegant solution?
Thank you.
Code:
Private Sub TextBox1_Change()
'Textval used as variable from user input
'Numval becomes textval providing the user input is numerical
Dim textval As String
Dim numval As String
textval = TextBox1.Text
If IsNumeric(textval) Then
numval = textval
Else
TextBox1.Text = CStr(numval)
End If
End Sub

Answer 1

code vb.net :
If Asc(e.KeyChar) <> 13 AndAlso Asc(e.KeyChar) <> 8 AndAlso Not IsNumeric(e.KeyChar) Then
' your code here
e.Handled = True
End If
and you can Replace text :
code :
Text = Text.Replace("string", "replace_by_this_string")

Answer 2

If the program requires the user to type only numeric data to the textbox, you should enforce the restriction when the user pressed a key
Use the textbox's KeyDown event:
'Omitting the parameters and Handles keyword
Private Sub textbox_KeyDown()
'Set the keys you would want to allow in this array
Dim allowedkeys As Keys() = {Keys.D1, Keys.D2, Keys.D3, Keys.D4, Keys.D5, Keys.D6, Keys.D7, Keys.D8, Keys.D9, Keys.D0, Keys.Back}
For i = 0 To allowedkeys.Length - 1 'Iterate through the allowed keys array
If e.KeyCode = allowedkeys(i) Then 'If the key pressed is present in the array...
Exit Sub 'The check returned a success. Exit and accept the key
End If
Next
e.SuppressKeyPress = True 'Supress all keys that failed the check
End Sub
Don't forget to add more keys that you need! The Space key, the numpad keys, the dot (point) keys?
This way you can remove the check in the Changed event and go directly to numval = textval
Or for those lazy programmers, numval = TextBox1.Text and numval = Val(TextBox1.Text) worked as well