How to make replacement with Regular Expressions

This simple example shows how to use Regular Expressions for replacing pattern of string.

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Text

Imports System.Windows.Forms
Imports System.Text.RegularExpressions

Namespace WindowsApplication1
    Partial Public Class Form1
        Inherits Form
        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs)
            Dim digitrex As Regex = New Regex("(?<digit>[0-9])")
            Dim text1 As String = textBox1.Text.ToString()
            Dim resulttext As String = digitrex.Replace(before, "")
            textBox2.Text = resulttext
        End Sub
    End Class
End Namespace