FileUpload控件打开图像文件后（上传前），如何在image控件中显示

我的页面上有3个控件：image、fileupload、button（图片提交按键）
运行时，在点击fileupload的“浏览”键后，希望在iamge中也显示，请问如何实现？谢谢！给出先有代码：protected void Page_Load(object sender, EventArgs e)
        {
            if (File.Exists(@"D:\wwwnew\tupianshangchuan\tupianshangchuan\image\179.jpg") == false) //不存在该图片文件
            {
                Image1.ImageUrl = Server.MapPath("~/image/") + "179.jpg";
            }
            else //存在该图片文件
            {
                Image1.ImageUrl = Server.MapPath("~/image/") + "touxiang.jpg";
            }

        }        protected void Button1_Click(object sender, EventArgs e)
        {
            bool Files = false;
            //判断文件的类型是否符合要求
            if (this.FileUpload1.HasFile)
            {
                //获取删除文件的后缀
                string fileSuffix = System.IO.Path.GetExtension(this.FileUpload1.FileName).ToLower();
                string[] Suffix = { ".jpg", ".bmp", ".gif", ".png" };
                //判断文件是否符合要求
                for (int i = 0; i < Suffix.Length; i++)
                {
                    if (fileSuffix == Suffix[i])
                    {
                        Files = true;
                    }
                }
            }            //如果符合要求就上传,并显示信息
            if (Files == true)
            {
                //this.Image1.ImageUrl = "~/imager/" + FileUpload1.FileName;
                this.Image1.ImageUrl = FileUpload1.FileName;
                this.FileUpload1.SaveAs(Server.MapPath("~/image/") + FileUpload1.FileName);
                // this.FileUpload1.SaveAs(Request.PhysicalApplicationPath+"\\"+"123\\" + FileUpload1.FileName);
            }
            else
            {
                Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "<script language='javascript' defer>alert('文件上传失败！');</script>");            }
}

解决方案 »

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这一篇很好:
http://topic.csdn.net/u/20091224/16/f37b7c72-0aaf-4e9d-9bd5-9af1fefd48be.html?40917
<script language="javascript" type="text/javascript">
        function PreviewImg(imgFile)
        {
            var newPreview = document.getElementById("newPreview");
            newPreview.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgFile.value;
            newPreview.style.width = "80px";
            newPreview.style.height = "60px";
        }
    </script>
<asp:FileUpload ID="FileUpload1" runat="server" onchange="PreviewImg(this)"  />
<div id="newPreview"> </div>
function $(o){return document.getElementById(o);}
function CheckImg(o,img)
{
    if (!/\.((jpg)|(bmp)|(gif)|(png))$/ig.test(o.value))
    {
        alert('只能上传jpg,bmp,gif,png格式图片!');
        o.outerHTML = o.outerHTML;
    }
    else
    {
        $(img).filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src=o.value;
    }
} <asp:FileUpload ID="FileUpload1" runat="server"  onchange="CheckImg(this, 'img');"  />
<div id="img" style="filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src= <%= pic%>,sizingMethod=scale);width:88px;height:113px;"> </div>
public string pic="";
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>上传图片前预览(兼容Firefox3,IE6,IE7,IE8)</title>
<style type="text/css">
#preview_wrapper{
    display:inline-block;
    width:300px;
    height:300px;
    background-color:#CCC;
}
#preview_fake{ /* 该对象用户在IE下显示预览图片 */
    filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale);
}
#preview_size_fake{ /* 该对象只用来在IE下获得图片的原始尺寸，无其它用途 */
    filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);
    visibility:hidden;
}
#preview{ /* 该对象用户在FF下显示预览图片 */
    width:300px;
    height:300px;
}
</style><script type="text/javascript">
function onUploadImgChange(sender){
    if( !sender.value.match( /.jpg|.gif|.png|.bmp/i ) ){
        alert('图片格式无效！');
        return false;
    }

    var objPreview = document.getElementById( 'preview' );
    var objPreviewFake = document.getElementById( 'preview_fake' );
    var objPreviewSizeFake = document.getElementById( 'preview_size_fake' );

    if( sender.files && sender.files[0] ){
        objPreview.style.display = 'block';
        objPreview.style.width = 'auto';
        objPreview.style.height = 'auto';

        // Firefox 因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
        objPreview.src = sender.files[0].getAsDataURL();
    }else if( objPreviewFake.filters ){
        // IE7,IE8 在设置本地图片地址为 img.src 时出现莫名其妙的后果
        //（相同环境有时能显示，有时不显示），因此只能用滤镜来解决

        // IE7, IE8因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
        sender.select();
        var imgSrc = document.selection.createRange().text;

        objPreviewFake.filters.item(
            'DXImageTransform.Microsoft.AlphaImageLoader').src = imgSrc;
        objPreviewSizeFake.filters.item(
            'DXImageTransform.Microsoft.AlphaImageLoader').src = imgSrc;

        autoSizePreview( objPreviewFake,
            objPreviewSizeFake.offsetWidth, objPreviewSizeFake.offsetHeight );
        objPreview.style.display = 'none';
    }
}  function onPreviewLoad(sender){
    autoSizePreview( sender, sender.offsetWidth, sender.offsetHeight );
}  function autoSizePreview( objPre, originalWidth, originalHeight ){
    var zoomParam = clacImgZoomParam( 300, 300, originalWidth, originalHeight );
    objPre.style.width = zoomParam.width + 'px';
    objPre.style.height = zoomParam.height + 'px';
    objPre.style.marginTop = zoomParam.top + 'px';
    objPre.style.marginLeft = zoomParam.left + 'px';
}  function clacImgZoomParam( maxWidth, maxHeight, width, height ){
    var param = { width:width, height:height, top:0, left:0 };

    if( width>maxWidth || height>maxHeight ){
        rateWidth = width / maxWidth;
        rateHeight = height / maxHeight;

        if( rateWidth > rateHeight ){
            param.width = maxWidth;
            param.height = height / rateWidth;
        }else{
            param.width = width / rateHeight;
            param.height = maxHeight;
        }
    }

    param.left = (maxWidth - param.width) / 2;
    param.top = (maxHeight - param.height) / 2;

    return param;
}
</script></head>
<body>
    <form id="form1" runat="server">
    <div>
    <table style="width: 307px">
        <tr>
            <td colspan="3" rowspan="3">
               <div id="preview_wrapper">
        <div id="preview_fake">
            <img src="" alt="图片预览" id="preview" onload="onPreviewLoad(this)"/>
        </div>
    </div> </td>
        </tr>
        <tr>
        </tr>
        <tr>
        </tr>
    </table>
    <br/>
     
        <asp:FileUpload ID="FileUpload1" runat="server" onchange="onUploadImgChange(this)"/><br/> 
        
    <img src="" alt="图片预览" id="preview_size_fake"/> 
    </div>
    </form>
</body>
</html>//
//把这句：<asp:FileUpload ID="FileUpload1" runat="server" onchange="onUploadImgChange(this)"/>
//改为：<asp:FileUpload ID="FileUpload1" runat="server" />
//在后台：
//protected void Page_Load(object sender, EventArgs e)
    {
        FileUpload1.Attributes.Add("onchange", " onUploadImgChange(this) ");
    }
//就不会出现：
<script>
   function show(obj){
      document.getElementById("imgtest").src=obj.value;
   }
</script>
<img src="" id="imgtest" />
<asp:FileUpload ID="FileUpload1" runat="server" onchange="show(this)"/>