您在OnClick事件中调用它
您需要在OnClientClick上调用它.

Your Calling it on OnClick event
you need to call that on OnClientClick.

正如mahen25所说，您需要在onclientclick事件中调用

As mahen25 said you need to call in onclientclick event

<asp:Button ID="Button1" runat="server" onclientclick="message()" Text="Button"/>

如果要调用函数服务器端，则需要在页面加载中注册Onclick事件.

You need to register the Onclick event in pageload if you want to call the function server side.

Button1.Attributes.Add("OnClick","message()");