限制TextBox框 所输入的字符数

<asp:textbox id="TextBox4" name="TextBox4" CssClass="batextarea" onpropertychange="if(value.length>100)value=value.substr(0,100)" cols="4" runat="server" rows="4" Height="153px" Width="500px" TextMode="MultiLine" MaxLength="100"></asp:textbox></td>