ASP.NET

 Public Sub Alert(ByVal argMessage As String)
        sb = New StringBuilder
        sb.Append("<script>")
        sb.Append("alert('")
        sb.Append(argMessage)
        sb.Append("');")
        sb.Append("</script>")
        <big>Page.ClientScript.RegisterStartupScript(Me.GetType(), "Message", sb.ToString())</big>    
-- I've tried to change this into RegisterClientScriptBlock , but its the same result.
End Sub

 Protected Sub btnSearch_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSearch.Click

	.... my query here.....

       If ds.Tables(0).Rows.Count = 0 Then
                Me.Alert("No data found.pease search again.")
                Return  --> ' i tried to remove this, but its the same result.
        End If

End Sub