client side scriptblock are not working in my pages.

Protected Sub Delete_onGridRow_Click(ByVal sender As Object, ByVal e As EventArgs)
       Try
           ostate = New BLstate

           str = DirectCast(sender, System.Web.UI.WebControls.ImageButton).CommandName.ToString
           With ostate
               .stateid = str
           End With

           result = state.state_delete(ostate)

           If result > 0 Then
               gvList.DataSource = state.Listview(txtstate.Text, ddstateStatus.SelectedValue)
               gvList.DataBind()
               'Page.ClientScript.RegisterClientScriptBlock(Me.GetType, "alert", "alert('item not deleted');", True)
               'Page.ClientScript.RegisterStartupScript(Me.GetType, "alert", "showDialog('Warning','Item not deleted.','warning');", True)
               'Response.Write("item not deleted")
               ScriptManager.RegisterStartupScript(Me, Me.GetType, "alert",script, True)

           End If

       Catch ex As Exception
           MsgBox(ex.Message)
       End Try
   End Sub