MESSAGE BOX CLASS

public void MessageBox(System.Web.UI.Page page, string Msg)
    {
        string MsgScript = "<script language='javascript'>alert('" + Msg + "')</script>";
        if (!(page.IsStartupScriptRegistered("MessageScript")))
            page.RegisterStartupScript("MessageScript", MsgScript);

    }

USE:
MessageBox(this, "Try Again");