その２

ちょっと変えた→修正版３

Option Strict On

Option Explicit On
Imports System.Web.UI

Imports System.Web.UI.WebControls

Imports AjaxControlToolkit
Public Class カスタムコントロール

    Inherits TextBox
    Private Sub カスタムコントロール_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender

        Dim _scriptManager As ScriptManager = ScriptManager.GetCurrent(Me.Page)

        For Each script As ScriptReference In ScriptObjectBuilder.GetScriptReferences(GetType(FilteredTextBoxExtender))

            _scriptManager.Scripts.Add(script)

        Next
        Dim registerScript As String = _

            "Sys.Application.add_init(function() {" & _

            "  $create(AjaxControlToolkit.FilteredTextBoxBehavior, " & _

                         " { 'FilterType':" & "2," & _

                         "   'id'        :'" & Me.ClientID & "_FilteredTextBoxExtender'}" & _

                         ", null, null, $get('" & Me.ClientID & "'))" & _

            "});"

        ScriptManager.RegisterStartupScript(Me.Page, GetType(String), Me.ClientID & "FileterdScript", registerScript, True)

    End Sub

End Class