程序代码：

function createJs(src) {
    if (document.getElementById("wyhSS")) {
        alert('请不要重复点击标签');
        return
    };
    var Scrip = document.createElement("script");
    Scrip.id = "wyhSS";
    Scrip.src = src;
    document.body.appendChild(Scrip)
};

程序代码：

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication1
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string str = Request["str"].ToString();

            this.Page.ClientScript.RegisterStartupScript(this.Page.GetType(), "", "<script>createJs(" + str + ");</script>", true);
        }
    }
}