Getting error from Isnumeric() VB.NET - vb.net

Question

I'm getting runtime error when I enter alphabets in the inputbox
Dim amount As String
amount = InputBox("Enter the amount of people you want to participtate", "System Message")
If amount < 0 Or Not (IsNumeric(amount)) Then
MsgBox("Please enter positive number of people", vbExclamation, "System Message")
End If

Answer 1

Comparing strings to numbers is pretty dangerous and blew up in your face. You can make it work but you'll have to code is carefully, ensuring that you never try to compare a string that can't be converted to a number. That requires using another operator:
If Not IsNumeric(amount) OrElse amount < 0 Then
MsgBox("Please enter positive number of people", vbExclamation, "System Message")
End If
Note the changed order and the use of OrElse, the short-circuiting version of Or. It won't evaluate the right-hand side expression if the left-hand side is already True.
The more .NET centric way to do this is by using Integer.TryParse() to convert strings to numbers.

Answer 2

To avoid an error, you can make it like this ..
If IsNumeric(amount) Then
If value(amount) > 0 Then
'codes here
Else
MsgBox("Please enter positive number of people", vbExclamation, "System Message")
End If
Else
MsgBox("Please enter a number of people", vbExclamation, "System Message")
End If

Answer 3

So I was looking at validating a textbox, first I wanted to make sure that it was not empty and make sure that it was a number. I'm by no means an expert but I'll put the code I wrote to validate the user input. I put it in a function because I had a lot of text fields that the user had to enter.
Class MainWindow
Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
tb2.Text = tbCheck(tb1)
End Sub
Private Function tbCheck(ByRef tb As TextBox) As Boolean
tbCheck = tb.Text.Length > 0
Try
tbCheck = (tb.Text / 1) > 0
Catch ex As Exception
tbCheck = False
End Try
Return tbCheck
End Function
End Class
This is just the simple program I wrote to check if the code worked as I had hoped.
Hope this can help someone or at least tell me if there is something I'm missing.