Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        TextBox1.Text = "I Enjoy ASP.NET"
 
        Dim myscript As String = "alert(document.getElementById('TextBox1').value);"
        Page.ClientScript.RegisterStartupScript(Me.GetType(), "myscript", myscript, True)
    End Sub
 
    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim strMessage As String
        strMessage = "Hi, You clicked ClickMe button"
        Dim strScript As String = "<script language=JavaScript>"
        strScript += "alert('" & strMessage & "');"
        strScript += "</script>"
 
        If (Not ClientScript.IsStartupScriptRegistered("clientScript")) Then
            ClientScript.RegisterClientScriptBlock(Me.GetType(), "clientScript", strScript)
        End If
    End Sub