预防按钮的多次点击，预防恶意刷新

<asp:button runat="server" ID="btn" text="Button" OnClick="aa_Click" />

public void page_load(Object obj,EventArgs e) 

{ 

  btn.Attributes.Add("onclick","state=true;"); 

  StringBuilder sb=new StringBuilder(); 

  sb.Append("if (!state) return;"); 

  sb.Append("var button=document.getElementById('btn');"); 

  sb.Append("button.value='Please Wait...';"); 

  sb.Append("document.body.style.cursor='wait';"); 

  sb.Append("button.disabled=true;"); 

  string strScript="<script>"; 

  strScript=strScript +"var state=false;"; 

  //将函数绑定到页面的onbeforeunload事件: 

  strScript=strScript +"window.attachEvent('onbeforeunload',function(){" +sb.ToString()+ "});"; 

  strScript=strScript +"</"+"script>"; 

  Page.RegisterStartupScript("onbeforeunload",strScript); 

} 

    protected void aa_Click(object sender, EventArgs e)

    {

        //模拟长时间的按钮处理 

        System.Threading.Thread.Sleep(2000);

        Response.Write("<script>alert('bbbbbb!!');" + "</" + "script>"); 

    }