asp.net 防恶意刷新 多次点击按钮的方法

前台：

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

 

后台

 

 

    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.ClientScript.RegisterStartupScript(typeof(_Default),"onbeforeunload", strScript);  //typeof(_Default)为默认的类名，要改的。
    }

    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>");
    }