Check the numerical value

[retkehing]

How to check the input of textbox.text whether is a numerical value or not?

 

[vis781]

microsoft.visualbasic.isnumeric(textbox.text)

I know it's part of the 'old' visual basic, but it really is a very efficient function.

 

[retkehing]

And how to express that textbox.text not equal to "" or equal to ""?

 

[vis781]

if textbox.text.equals(string.empty) then
'do whatever
end if

 

[Paszt]

Here's a good article: Benchmarking IsNumeric options.

 

[jmcilhinney]

You should use Double.TryParse. It was specifically created to improve the perfromance of IsNumeric. If IsNumeric is going to call it anyway then why not do it yourself? It also gives you the ability to specify the types of numbers that are acceptable, like only positive, only integers or only currency.

        Dim num As Double

        If Double.TryParse(Me.TextBox1.Text, Globalization.NumberStyles.Float, Nothing, num) Then
            MessageBox.Show("You entered the number " & num.ToString())
        Else
            MessageBox.Show("Please enter a valid number.")
        End If