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 = " width: 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>