1、C#调用JavaScript

（1）准备好JavaScript函数

       <script type="text/javascript">

               function say() {

                   alert("CSharp调用js，调用成功！");

               }

      </script>

（2）页面代码
<asp:Button ID="Button1" runat="server" Text="CSharp调用js" onclick="Button1_Click" />
（3）C#代码
    protected void Button1_Click(object sender, EventArgs e)
    {
        Page.ClientScript.RegisterStartupScript(ClientScript.GetType(), "say", "<script>say(); </script>");
    }
2、JavaScript调用C#代码

（1）页面代码

        <input type="button" value="js调用CSharp" onclick="jsCallCSharp();" />
        <asp:Button ID="Button2" runat="server" Text="我是隐藏按钮" onclick="Button2_Click" style="display:none;"/>
（2）C#代码

    //后台方法
    public void Show()
    {
        Response.Write("js调用后台方法成功！");
    }
    //隐藏按钮事件
    protected void Button2_Click(object sender, EventArgs e)
    {
        Show();
    }

（3）JavaScript代码

           <script type="text/javascript">
  
               function jsCallCSharp() {

                   document.getElementById("Button2").click();

               }

      </script>