<form id= "form1 " runat= "server " onsubmit= "return checkdata() ">
<asp:Button ID= "Button2 " runat= "server " UseSubmitBehavior= "false " Text= "检查用户名是否可用 " >
每次点击，都会触发checkdata(),设置UseSubmitBehavior= "false "不起作用，请高手回答
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给它注册一个Click客户端事件,在这个事件里return false应该可以吧.
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Button2.Attributes.Add( "onclick ", "return false; ");
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<asp:Button ID= "Button2 " runat= "server " OnClientClick= "return false " UseSubmitBehavior= "false " Text= "检查用户名是否可用 " />