将页面上的回车事件绑定到某个按钮上:
1.先实现按钮的事件
2.textbox 添加按钮事件
this.mytext.Attributes.Add("onkeydown",
                "if(event.which || event.keyCode){if ((event.which == 13) || (event.keyCode == 13)) {document.getElementById('" + btnSend.UniqueID + "').click();return false;}} else {return true}; ");