MessageBox.Show on no input in Label?

[RoccoSiffredi]

I want the messagebox.show to display an error message if there is no input in a label :

If (txtdays.Text > 100) And (txtdays.Text = "") Then MessageBox.Show("Please enter a value between 1 and 100")

There are no errors in the code but if there is no input in the txtdays label VBE hangs. What am I doing wrong?

 

[Andrzejek]

If (txtdays.Text > 100) And (txtdays.Text = "") Then

This statement can never be true: you will never have both conditions met. You can NOT have a value in your text box of 250 and the text box be ampty at the same time.

Try:

If ([blue]Val[/blue](txtdays.Text) > 100) [blue]Or[/blue] (txtdays.Text = "") Then

Have fun.

---- Andy

 

[RoccoSiffredi]

Thanks but it sill hangs.

 

[Andrzejek]

What do you measn by 'sill hangs'?

One simple Form, text box named txtdays and a command button:

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Button1.Click
        If (Val(txtdays.Text) > 100) Or (txtdays.Text = "") Then
            MessageBox.Show("Please enter a value between 1 and 100")
        End If
    End Sub
End Class

VB.NET 2008, works like a dream

Have fun.

---- Andy

 

[RoccoSiffredi]

Thanks Andy. I created a new form with your code and it works. What I want to do is give errors if :

There is no input
There is not a numerical input
The value entered is over 100

For some reason this works but I don't understand why :

If Not (IsNumeric(txtdays.Text) > 100) Or txtdays.Text = "" Then

Can someone explain why that works and this doesn't? :

If Not (IsNumeric(txtdays.Text) Or txtdays.Text = "" Or txtdays.Text > 100 Then
MessageBox.Show("Please enter a value between 1 and 100")
End If

 

[RoccoSiffredi]

Actually it doesn't work, it produces errors even if the value entered is below 100.

 

[Andrzejek]

Well, you have to be more specific.

If you say "Actually it doesn't work" - you need to specify what is it, which piece of code does not work?

Have fun.

---- Andy

 

[Andrzejek]

This code works like a dream (again)

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles Button1.Click
[blue]
        If Not (IsNumeric(txtdays.Text)) Or _
        txtdays.Text = "" Or _
        Val(txtdays.Text) > 100 Then
            MessageBox.Show("Please enter a value between 1 and 100")
        End If
[/blue]
    End Sub
End Class

Have fun.

---- Andy

 

[Andrzejek]

If you are talking about his code:

If [red]Not[/red] ([blue]IsNumeric(txtdays.Text)[/blue] > 100) Or txtdays.Text = "" Then

then you need to know a little about the IF-THEN statement.

If you type 25 in your txtdays text box, first it is evaluated IsNumeric (blue portion of the code), which it is - TRUE. Then you change it to FALSE by the Not operator (red code). Then it does not latter if [tt]txtdays.Text = ""[/tt] is TRUE or FALSE because the entire statement will be FALSE anyway.

Have fun.

---- Andy

 

[RoccoSiffredi]

Yep that did it. The issue was I had this after my dims :

days = txtdays.Text
months = months.Text
years = text.Text

In order to add the three values together. I moved them after the validation and it worked.

Thank you very much. Can you explain what 'Val' does? Haven't come across this before, only been learning the langue a short time.

 

[Andrzejek]

Sure,

If you type 25 in your text box, it is a text, not a number. Your computer sees it as "25", the same way as "abc" or "99 botles of beer on the wall".

[tt]Val()[/tt] function converts "25" text to a value of 25 - a number, so you can compare it to another number.

Have fun.

---- Andy

 

[RoccoSiffredi]

Thanks.

 

[Sorwen]

I'm a little late to the game, but one thing to note this is wrong:

IsNumeric(txtdays.Text) > 100

IsNumeric returns True (-1) and False (0) so it will always be less than 100.

-I hate Microsoft!
-Forever and always forward.
-My kingdom for a edit button!

 

[realm174]

Good catch Sorwen!!

Cheers,

Realm174

 

[RoccoSiffredi]

Can someone recommend a VBA book or resource listing commands and their parameters?