Minecraft Name Generator

Imports System.IO
Imports System.Net

Public Class Form1
    Dim count As Integer = 0
    Private Function checkName(ByVal name As String) As Boolean
        count += 1
        Label3.Text = "Requests Sent: " & count

        Dim address As String = "https://minecraft.net/haspaid.jsp?user=" & name
        Dim client As WebClient = New WebClient()
        Dim reader As StreamReader = New StreamReader(client.OpenRead(address))
        RichTextBox1.Text = reader.ReadToEnd
        If RichTextBox1.Text = True Then
            Return False
        End If
        Return True
    End Function

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        ListBox1.Items.Clear()
        ProgressBar1.Value = 0

        If RadioButton1.Checked Then
            Do While ListBox1.Items.Count < CInt(TextBox1.Text)
                Dim s As String = lettersOnly(3, False)
                If checkName(s) = True Then
                    ListBox1.Items.Add(s)
                    ProgressBar1.Value += 1
                End If
            Loop
            MsgBox("Done")
            ProgressBar1.Value = ProgressBar1.Value
        End If
        If RadioButton2.Checked Then
            Do While ListBox1.Items.Count < CInt(TextBox1.Text)
                Dim s As String = numbersOnly(3, False)
                If checkName(s) = True Then
                    ListBox1.Items.Add(s)
                    ProgressBar1.Value += 1
                End If
            Loop
            MsgBox("Done")
            ProgressBar1.Value = ProgressBar1.Value
        End If
        If RadioButton3.Checked Then
            Do While ListBox1.Items.Count < CInt(TextBox1.Text)
                Dim s As String = both(3, False)
                If checkName(s) = True Then
                    ListBox1.Items.Add(s)
                    ProgressBar1.Value += 1
                End If
            Loop
            MsgBox("Done")
            ProgressBar1.Value = ProgressBar1.Value
        End If
        If RadioButton4.Checked Then
            Do While ListBox1.Items.Count < CInt(TextBox1.Text)
                Dim s As String = all(3, False)
                If checkName(s) = True Then
                    ListBox1.Items.Add(s)
                    ProgressBar1.Value += 1
                End If
            Loop
            MsgBox("Done")
            ProgressBar1.Value = ProgressBar1.Value
        End If
    End Sub

    Public Function both(ByRef len As Integer, ByRef upper As Boolean) As String
        Dim rand As New Random()
        Dim allowableChars() As Char = "abcdefghijklmnopqrstuvwxyz1234567890".ToCharArray()
        Dim final As String = String.Empty
        For i As Integer = 0 To len - 1
            final += allowableChars(rand.Next(allowableChars.Length - 1))
        Next

        Return IIf(upper, final.ToUpper(), final)
    End Function

    Public Function lettersOnly(ByRef len As Integer, ByRef upper As Boolean) As String
        Dim rand As New Random()
        Dim allowableChars() As Char = "abcdefghijklmnopqrstuvwxyz".ToCharArray()
        Dim final As String = String.Empty
        For i As Integer = 0 To len - 1
            final += allowableChars(rand.Next(allowableChars.Length - 1))
        Next

        Return IIf(upper, final.ToUpper(), final)
    End Function

    Public Function numbersOnly(ByRef len As Integer, ByRef upper As Boolean) As String
        Dim rand As New Random()
        Dim allowableChars() As Char = "1234567890".ToCharArray()
        Dim final As String = String.Empty
        For i As Integer = 0 To len - 1
            final += allowableChars(rand.Next(allowableChars.Length - 1))
        Next

        Return IIf(upper, final.ToUpper(), final)
    End Function

    Public Function all(ByRef len As Integer, ByRef upper As Boolean) As String
        Dim rand As New Random()
        Dim allowableChars() As Char = "abcdefghijklmnopqrstuvwxyz1234567890_".ToCharArray()
        Dim final As String = String.Empty
        For i As Integer = 0 To len - 1
            final += allowableChars(rand.Next(allowableChars.Length - 1))
        Next

        Return IIf(upper, final.ToUpper(), final)
    End Function

    Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.Validated
        ProgressBar1.Maximum = CInt(TextBox1.Text)
    End Sub
End Class