c#.net&js web开发中常用代码

一：checkbox全选以及反选：

特殊

二：上传文件时显示缩略图

<script language="JavaScript">
var flag=false;
function DrawImage(ImgD){
   var image=new Image();
   image.src=ImgD.src;
   if(image.width>0 && image.height>0){
    flag=true;
    if(image.width/image.height>= 120/80){
     if(image.width>120){  
     ImgD.width=120;
     ImgD.height=(image.height*120)/image.width;
     }else{
     ImgD.width=image.width;  
     ImgD.height=image.height;
     }
     ImgD.alt=image.width+"×"+image.height;
     }
    else{
     if(image.height>80){  
     ImgD.height=80;
     ImgD.width=(image.width*80)/image.height;     
     }else{
     ImgD.width=image.width;  
     ImgD.height=image.height;
     }
     ImgD.alt=image.width+"×"+image.height;
     }
    }
   /**//*else{
    ImgD.src="";
    ImgD.alt=""
    }*/
   } 

function FileChange(Value){
flag=false;
document.all.uploadimage.width=10;
document.all.uploadimage.height=10;
document.all.uploadimage.alt="";
document.all.uploadimage.src=Value;
}

function BeforeUpLoad(){
if(flag) alert("OK");else alert("FAIL");
}
    </script>

    <input style=" 143px; height: 18px" type="file" size="8" name="pic" onchange="javascript:FileChange(this.value);">
    <img id="uploadimage" height="10" width="10" src="" onload="javascript:DrawImage(this);"><br>
    <button onclick="javascript:BeforeUpLoad();">
        提交</button>