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IsNaN in VB help-VBForums
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Thread: IsNaN in VB help

  1. #1

    Thread Starter
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    IsNaN in VB help

    i have a text box called write.text

    when someone inputs a alphabet letter i need a pop up box to appear

    If IsNaN write.text Then
    Console.WriteLine("please input numbers only")
    Else
    End If

  2. #2
    Super Moderator dday9's Avatar
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    Re: IsNaN in VB help

    In the TextChanged event you could use the TryParse event:
    Code:
    If Not Integer.TryParse(write.Text, Nothing) Then
        MessageBox.Show("Please input numbers only.")
    End If
    Alternatively you could use a NumericUpDown control instead.

  3. #3

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    Re: IsNaN in VB help

    how would you do it if i put

    Dim write As Decimal
    write = write.Text
    If Not Decimal.TryParse(write, Nothing) Then
    msg(hi)

  4. #4
    PowerPoster SJWhiteley's Avatar
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    Re: IsNaN in VB help

    Quote Originally Posted by philbob View Post
    how would you do it if i put

    Dim write As Decimal
    write = write.Text
    If Not Decimal.TryParse(write, Nothing) Then
    msg(hi)
    What does the documentation say about Decimal.TryParse? It tells you how to use it.
    "Ok, my response to that is pending a Google search" - Bucky Katt.
    "There are two types of people in the world: Those who can extrapolate from incomplete data sets." - Unk.
    "Before you can 'think outside the box' you need to understand where the box is."

  5. #5
    Hyperactive Member Vexslasher's Avatar
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    Re: IsNaN in VB help

    If your only wanting them to input numbers then you could just do away with the ability to use letters and special characters.

    This will make the write.text only be allowed to have digits 0-9 and , .
    vb.net Code:
    1. Private Sub write_TextChanged(sender As Object, e As EventArgs) Handles write.TextChanged
    2.         write.Text = System.Text.RegularExpressions.Regex.Replace(write.Text, "[A-Za-z/w]", "")
    3.         If Not Double.TryParse(write.Text, Nothing) AndAlso write.Text.Length <> 0 Then
    4.             write.Text = write.Text.Substring(0, write.Text.Length - 1)
    5.         End If
    6.         write.Select(write.Text.Length, 0)
    7.     End Sub

  6. #6
    Super Moderator Shaggy Hiker's Avatar
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    Re: IsNaN in VB help

    You should really be using a NumericUpDown control, which would prevent the problem entirely.
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