Get a textbox to accept only characters in vb.net - vb.net

Question

I'm creating a simple application in Vb.net where I need to perform certain validations. So I want a name textbox to accept only characters from a-z and A-Z for example.
For this I wrote the following code:
Private Sub txtname_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox5.KeyPress
If Asc(e.KeyChar) <> 8 Then
If Asc(e.KeyChar) > 65 Or Asc(e.KeyChar) < 90 Or Asc(e.KeyChar) > 96 Or Asc(e.KeyChar) < 122 Then
e.Handled = True
End If
End If
End Sub
But somehow it is not allowing me to enter characters. When I try to enter any character it does nothing.
What causes this problem and how can I resolve it?

Answer 1

Alternatively, you can do something like this,
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) _
Handles txtName.KeyPress
If Not (Asc(e.KeyChar) = 8) Then
Dim allowedChars As String = "abcdefghijklmnopqrstuvwxyz"
If Not allowedChars.Contains(e.KeyChar.ToString.ToLower) Then
e.KeyChar = ChrW(0)
e.Handled = True
End If
End If
End Sub
or if you still want the ASCII way, try this,
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtName.KeyPress
If Not (Asc(e.KeyChar) = 8) Then
If Not ((Asc(e.KeyChar) >= 97 And Asc(e.KeyChar) <= 122) Or (Asc(e.KeyChar) >= 65 And Asc(e.KeyChar) <= 90)) Then
e.KeyChar = ChrW(0)
e.Handled = True
End If
End If
End Sub
both will behave the same.

Answer 2

This is a more abstract approach, but still effective nonetheless. It's straightforward and can just be added to the TextChanged event. You can use it with multiple textboxes by adding their handles to the sub and using a DirectCast().
Dim allowed As String = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
For Each c As Char In TextBox.Text
If allowed.Contains(c) = False Then
TextBox.Text = TextBox.Text.Remove(TextBox.SelectionStart - 1, 1)
TextBox.Select(TextBox.Text.Count, 0)
End If
Next
Summary: If an invalid character is entered, it will immediately be deleted (most of the time the character won't be visible long enough for the user to notice).

Answer 3

Private Sub txtname_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox5.KeyPress
If AscW(e.KeyChar) > 64 And AscW(e.KeyChar) < 91 Or AscW(e.KeyChar) > 96 And AscW(e.KeyChar) < 123 Or AscW(e.KeyChar) = 8 Then
Else
e.KeyChar = Nothing
End If
End Sub
I hope this helps!

Answer 4

Am using below code to accept only letters, "-" or "'" when user is entering a person name (maybe it is simple and easier):
Private Sub txtEName1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtEName1.KeyPress
If Char.IsLetter(e.KeyChar) Or e.KeyChar = vbBack Or e.KeyChar = "-" Or e.KeyChar = "'" Then
e.Handled = False
Else
e.Handled = True
End If
End Sub
I allowed the backspace in order to allow the user to remove letters in case of mistakes

Answer 5

Private Sub txtStudentName_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtStudentName.KeyPress
If Not Char.IsLetter(e.KeyChar) And Not e.KeyChar = Chr(Keys.Delete) And Not e.KeyChar = Chr(Keys.Back) And Not e.KeyChar = Chr(Keys.Space) Then
e.Handled = True
End If
End Sub