Server side validation in VB

Question

I am trying to do a server side validation that blocks "^$/()|?+[]{}><" metacharacters Anyone give me some insight on why this . I am new to this :/ (TextBox3 is a asp textboxe that takes input)

Imports System.Text.RegularExpressions

Partial Class Default2
Inherits System.Web.UI.Page

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click

    If Regex.IsMatch(TextBox3.Text, "^$\/()|?+[]{}><") Then
        Label1.Text = "Invalid input"

    End If
End Sub
End Class

ERROR:

 Exception Details: System.ArgumentException: parsing "^$\/()|?+[]{}><" - Unterminated     [] set.

Answer 1

That's because the string ^$\/()|?+[]{}>< is regex metacharacters. You need to escape them before passing to the regex function:

    If Regex.IsMatch(TextBox3.Text, Regex.Escape("^$\/()|?+[]{}><")) Then
        Label1.Text = "Invalid input"
    End If

UPDATED ANSWER:

2 methods to check if the text contains any of the regex metacharacters:

Method 1: Using Regex

The metacharacters need to be put inside a character class [...]. Therefore, only some of the characters need to be escaped, ie: ^, \ and ].

    If Regex.IsMatch(TextBox1.Text, "[\^$\\/()|?+[\]{}><]") Then
        ' Invalid input
    Else
        ' Valid
    End If

Method 2: Using IndexOfAny String function

This method doesn't use Regex so, there is no need to escape.

    If TextBox1.Text.IndexOfAny("^$\/()|?+[]{}><".ToCharArray) > -1 Then
        ' Invalid input
    Else
        ' Valid
    End If