is letter or digit - textbox characters..

[gmatteson]

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?

[Lunatic3]

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...

[gmatteson]

do you know what that asci range will be?

[Lunatic3]

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

[Edneeis]

You could use RegularExpressions:

'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

[Lunatic3]

Originally posted by Edneeis
You could use RegularExpressions:

'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?

[Pirate]

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 :

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

[Edneeis]

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.

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

But whatever works, its all good.

[dynamic_sysop]

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

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