is letter or digit - textbox characters..

how can i tell if a user entered in ONLY a letter a-z and or a digit...

ive tried..

Dim mytext As Char
If mytext.IsLetterOrDigit(txtDistrictDB.Text) = True Then
MsgBox("yes")
Else
MsgBox("no")
End If

but if i type in a character such as !@#$%^&*()_ it returns true also.....

it doesn't work if i try to get the characters in a text box, but if i type in one character than it works.. is there a way around it rather than looping through each character?

Do you want it to be checked one by one as the user enteres the letters? If so check for the ascii of character to be in range of a-Z (if u like to include capitals too) and also 0-9. But you may also like to trap Space, Back Space, delete...

do you know what that asci range will be?

a-z 97-122
A-Z is 65-90
0-9 is 48-57

You could use RegularExpressions:

VB Code:

'search for anything other than a-zA-z0-9
        If DirectCast(Regex.Matches(TextBox1.Text, "\W"), MatchCollection).Count > 0 Then
            MsgBox("Contains non alphanumeric chars")
        Else
            MsgBox("Contains only alphanumeric chars")
        End If

You'll need to import the regularexpressions namespace:

Imports System.Text.RegularExpressions

Quote:

---

Originally posted by Edneeis
You could use RegularExpressions:

VB Code:

'search for anything other than a-zA-z0-9
        If DirectCast(Regex.Matches(TextBox1.Text, "\W"), MatchCollection).Count > 0 Then
            MsgBox("Contains non alphanumeric chars")
        Else
            MsgBox("Contains only alphanumeric chars")
        End If

You'll need to import the regularexpressions namespace:

Imports System.Text.RegularExpressions

---

Wouldn't that cause a performance problem if he want to check it real time-letter by letter- as Regex checks for the entire text each time?

Quote:

---

Originally posted by Lunatic3
Wouldn't that cause a performance problem if he want to check it real time-letter by letter- as Regex checks for the entire text each time?

---

I agree .

Here is how it should be done :

VB Code:

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        Dim KeyAscii As Integer
        KeyAscii = Asc(e.KeyChar)
 
        Select Case KeyAscii
            Case Asc(0) To Asc(9)
                MessageBox.Show("You entered number : " & e.KeyChar.ToString)
            Case (97) To (122)
                MessageBox.Show("You entered lowercase letter : " & e.KeyChar.ToString)
            Case (65) To (90)
                MessageBox.Show("You entered uppercase letter : " & e.KeyChar.ToString)
        End Select
 
    End Sub
End Class

RegularExpressions should be pretty fast but if he is checking letter by letter than it might. I must have misread I thought he didn't want to check letter by letter but instead the whole text at once.

Quote:

---

is there a way around it rather than looping through each character?

---

But whatever works, its all good.

all you need to do is this , to check if it's a letter / number or if it's another character :

VB Code:

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
 
        If e.KeyChar.IsLetterOrDigit(e.KeyChar) Then
            MessageBox.Show("is a letter or number")
        Else
            MessageBox.Show("is a character , not a number or letter!")
        End If
 
    End Sub

:)