this.box.Attributes["style"] = "display:block"; this.box.Attributes.Add("style", "display:block");
<div class="box" id="box" runat="server"> </div>
this.box.Attributes["style"] = "display:block"; this.box.Attributes.Add("style", "display:block");
<div class="box" id="box" runat="server"> </div>