FileUpload 上传图片前实现预览

前台代码：

    <form id="form1" runat="server">
        <div>
            <asp:FileUpload ID="file" runat="server" />

            <img id="img" style="display:none; width:120px; height:100px;" />

        </div>
    </form>

 

后台：

        protected void Page_Load(object sender, EventArgs e)
        {
            file.Attributes.Add("onchange", "document.getElementById('img').src=this.value;");
        }