Verify input data type

Question

Hi everyone, this is my first time messing with visual basic. I'm just learning how to do different things and right now I'm building a simple program to where the user inputs thier First and last name into two different text boxes and when they click on a button it tells them what they have entered.

I'm trying to make sure that they have entered letters only in each text box and if they don't I want it to display a message box that says they need to enter letters only. The problem I am having is if they enter a number in both text boxes then that is the only way that it will display the error message box. Here is my code for the data validation for the user input...

 

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles

Button1.Click

 

If IsNumeric(TextBox1.Text)

And

IsNumeric(TextBox2.Text)

Then

 

MessageBox.Show("I'm sorry, the data you entered is not of the correct type. Please enter leters only.", "Wrong Data Type Entered", MessageBoxButtons.OK, MessageBoxIcon

.Error)

 

Else

MsgBox(

"You have entered " & TextBox1.Text & " "

& TextBox2.Text)

 

End

If

 

End

Sub

 

 

Any help you can give would be much appreciated, thanks! 

Answer 1

Use Or in place or And, but what about if user enter space?

 

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Answer 2

Well that's another one of the things that I'm trying to figure out because I just tried entering nothing and it will display the message box without any user input. 

Is there a good way to code this as to where anything other than alphabetical letters or even nothing entered will display the error message box once the button is clicked?

Answer 3

IsNumeric will only return True if the text can be converted to a numeric value. If the text contains digits but they do not represent a valid number, IsNumeric will return False.

Use code like this:
        Dim TestText As String = TextBox1.Text & TextBox2.Text
        For Each c As Char In TestText
            If Char.IsDigit(c) Then
                MessageBox.Show("I'm sorry, the data you entered is not of the correct type. Please enter leters only.", "Wrong Data Type Entered", MessageBoxButtons.OK, MessageBoxIcon.Error)
                Exit Sub
            End If
        Next
        MsgBox("You have entered " & TextBox1.Text & " " & TextBox2.Text)

Note that your example does not agree with your description.   To be strictly as per your description the test should be:

        If Not Char.IsLetter(c) Then

Answer 4

Hi you can condition check if user has entered anything, if nothing or space then show error message otherwise show what they entered. You can use the textbox keypress to allow only what you want. Also there is validating event where you can force to remain in that control if user enter only space or nothing:)

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If String.IsNullOrWhiteSpace(TextBox1.Text) Or String.IsNullOrWhiteSpace(TextBox2.Text) Then
            MessageBox.Show("I'm sorry, the data you entered is not of the correct type. Please enter leters only.", "Wrong Data Type Entered", MessageBoxButtons.OK, MessageBoxIcon.Error)
        Else

            MsgBox("You have entered: " & StrConv(TextBox1.Text & ", " & TextBox2.Text, VbStrConv.ProperCase))

        End If

    End Sub

Just a thought my name can either be Xiong Wei, Jin or Xiongwei, Jin if the middle name is elimined then there are few hundreds whom has the same name, one time Blackwood has pointed out that there are people who has up to 4 or 5.^_^

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