asp.net แสดง messagebox ให้ alert บนเว็บ

Public Class MsgBox
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Not Page.IsPostBack() Then
			Page.RegisterClientScriptBlock("OnLoad", "<script>alert('Welcome to ThaiCreate.Com')</script>")
		End IF
    End Sub

    Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
			Page.RegisterClientScriptBlock("OnLoad", "<script>alert('Sawatdee " & Me.txtName.Text & "')</script>")
    End Sub

End Class