TextBox input limit codelet

In the student system, there are many input boxes, and the input content of each input box should not be the same. Some require the input of name, student ID, class, home address, etc. Because of the demand, it is necessary to limit the input content, the input of pure numbers, the input of pure text, etc. This requires us to use the code we learned before or the corresponding properties to limit.

The following are the main methods of restriction:

The limitation of code type, in fact, most of the input is the characters we type with the keyboard, so we can use ASCII code to limit the input content.

' Class number information can only be numbers

Private Sub txtClassno_KeyPress(KeyAscii As Integer)
       If KeyAscii = 8 Then Exit Sub
       If KeyAscii < 48 Or KeyAscii > 57 Then
          KeyAscii = 0
          MsgBox "Illegal characters, only numbers!", vbOKCancel, "Prompt"
       End If
     
       If Len(txtClassno) >= 3 Then
          txtClassno.Text = "" 'The content of the input box is cleared
             KeyAscii = 0 'The fourth character entered is cleared
           MsgBox "The number of digits entered is too long", vbOKCancel, "Prompt"
       End If
End Sub
'Do not support input of special symbols
Private Sub txtClassroom_KeyPress(KeyAscii As Integer)
If (KeyAscii >= 33 And KeyAscii <= 47) Or (KeyAscii >= 58 And KeyAscii <= 64) Or (KeyAscii >= 91 And KeyAscii <= 96) Or (KeyAscii >= 123 And KeyAscii <= 126) Then ( Note: Some of the punctuation characters have rounded and half-width distinctions. For example: full-width "," "." "·")
      KeyAscii = 0
      MsgBox "Special character input is not supported!", vbOKCancel, "Prompt"
      End If
End Sub
'Only enter letters and numbers
If KeyAscii = 8 Then Exit Sub
       If (KeyAscii >= 48 And KeyAscii <= 57) Or (KeyAscii >= 65 And KeyAscii <= 90) Or (KeyAscii >= 97 And KeyAscii <= 122) Then
          Else
          KeyAscii = 0
          MsgBox "Illegal characters, only letters or numbers!", vbOKCancel, "Prompt"
       End If
       If Len(txtold) >= 6 Then
           txtold.Text = "" 'The content of the input box is cleared
           KeyAscii = 0 'The fourth character entered is cleared
           MsgBox "Password entered is too long", vbOKCancel, "Prompt"
     End If

Input box input limit modification to frmmodifycourseinfo " modify course information " window