[RESOLVED] How to use Verification techniques on VB

[tushardevi]

Hello guys!



I am working on a project where I want to verify each field (see image). Someone who is fillling the form can only type letters in the First and Last name textbox and for the DOB(Date of Birth) I want the user to write it in the format of DD/MM/YYYY. If this requirements are not fulfilled then an error message box should appear with the right instructions.

1. I do not know how can I restrict the First and Last name textbox to letters only
2. I do not know how to change DOB format to DD/MM/YYYY

Could you please help me with the code.

Thank You.

[si_the_geek]

For date entry do not use a Textbox unless you are forced to.

To allow date entry it is much better to use a DateTimePicker instead, as not only does it force an appropriate format, it also ensures that only valid dates can be entered (eg: not 30th of February), allows a drop-down calendar if you want, and it allows you to directly extract the value as a Date rather than a String (which would need extra conversion and error handling if you want to store it as a Date).


Restricting a Textbox to letters only is a bit more awkward, as you need to deal with typing and pasting etc. A fairly simple way to do it is to have code in the Changed event that removes any non-letters, but it is awkward to get it perfect.

It is very likely that there are example(s) in our CodeBank forums of how to do it in a better way than I have described.

[ChrisE]

Hi,

like SI said use a Datetimepicker for the Date, as for Letters only
you could use this...

 Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        Dim Result As Boolean

        Result = CompareText_IsLetter(TextBox1.Text)
        Select Case Result
            Case True
                Label1.Text = Result.ToString() & " Input OK..."
            Case Else
                Label1.Text = Result.ToString() & " Input not allowed. Remove last entry"
        End Select
    End Sub
    Private Function CompareText_IsLetter(ByVal Source As String) As Boolean
        Dim n As Integer
        For n = 0 To Source.Length - 1
            If Not Char.IsLetter(Source.Chars(n)) Then
                Return False
            End If
        Next
        Return True
    End Function

regards
Chris

[4x2y]

You can also use KeyDown event to accept only keys you are interested in.

Private Sub TextBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles TextBox1.KeyDown, TextBox2.KeyDown
        Select Case e.KeyCode
            Case Keys.A To Keys.Z, Keys.Space, Keys.Delete, Keys.Back, Keys.Left, Keys.Right, Keys.Up, Keys.Down
                'Accept
            Case Else
                e.SuppressKeyPress = True
        End Select
    End Sub

[tushardevi]

sin_the_geek

I found a link on this website that tells you how to restrict certain characters from a text box
http://www.vbforums.com/showthread.p...ic-or-symbolic

I have played around with the code and just found out that the following lines are NOT actually needed to make the code work:
from the 1st code box:

Dim SelectionIndex As Integer = TextBox1.SelectionStart
Dim Change As Integer
Change = 1
FirstNameText.Select(SelectionIndex - Change, 0)

It works fine without these lines! I do not know why the coder used these lines. I am pretty sure that it has a use somewhere but can't figure out actually where!

I know TextBox1.SelectionStart workouts out the total number of letters in the string

But I don't understand what the other lines actually mean. Like why the coder has used a variable named "change"? And what does the line FirstNameText.Select(SelectionIndex - Change, 0) actually DO!?

Please explain why are these lines necessary, despite the fact that the code works perfectly fine without them!

Thank you

[4x2y]

These lines are important because they are preserve the caret position, to understand type an invalid letter, the caret will jump to the first position.

[tushardevi]

Cheers everyone for helping me!

[si_the_geek]

I know TextBox1.SelectionStart workouts out the total number of letters in the string

Nope, that would be .Text.Length

.SelectionStart tells you the start position of the Selection, and .SelectionLength tells you how long the selection is.

Usually the Selection is 0 characters (you just see the caret, and no text selected), but you can select text with the mouse (or by pressing Shift and using the cursor keys) to see it highlighted.

As 4x2y rightly pointed out, they (and .Select) are used in the code to make sure the caret keeps its position. It isn't the best example I've seen (because it doesn't also keep the selection if there was one), but it should be adequate.