1，文件的上传存在一个非常致命的文件，要是上传病毒文件，可能会使你的系统崩溃
所以判断文件的类型的非常重要的。
不能单独与后缀名判断，下面展示一种webform类型的上传文件案例。
1，书写html语言
<html> <head></head> <body> ?<li class="l-fieldcontainer" fieldindex="14"> ??<ul> ???<li style="width:120px;text-align:right;">*企业营业执照：</li> ???<li id="mainform|14" style="width:100px;text-align:left;"> ????<div class="l-text" style="width: 98px;"> ?????<input name="COMPANYLICENSE" validate="{"maxlength":300,"required":true}" class="l-text-field upper" style="width: 94px;" ligeruiid="COMPANYLICENSE" id="COMPANYLICENSE" type="text" /> ????</div></li> ???<li><img src="#" heigth="50px" id="updatePic" width="60px" /></li> ???<li> ????<form id="EditMenuForm" enctype="multipart/form-data"> ??????<input name="MenuPic" id="MenuPic" type="file" /> ?????<input name="btnUpload" id="btnUpload" value="上传" style="width:60px" type="button" /> ?????<label style="color:red">支持png,jpg格式图片，大小不能超过2M,必须清晰可见</label> ?????<label></label> ????</form></li> ???<li style="width:3px;"><span class="l-star">*</span></li> ??</ul></li> </body></html>
书写javasecript
ajaxSubmit的js文件来自：
?//上传图片 ???????????$(‘#btnUpload‘).click(function () { ???????????????if ($("#MenuPic").val()) { ???????????????????//让表单异步的提交到后台。 ???????????????????$("#EditMenuForm").ajaxSubmit({ ???????????????????????error: function (error) { alert(error); }, ???????????????????????url: ‘handler/validate.ashx‘, /*设置post提交到的页面*/ ???????????????????????type: "post", /*设置表单以post方法提交*/ ???????????????????????dataType: "text", /*设置返回值类型为文本*/ ???????????????????????data: { "Action": "PIC" }, ???????????????????????success: function (data) { ???????????????????????????if (data == "-1") { alert("图片大小不能超过2M"); return; } ???????????????????????????if (data == "-2") { alert("图片格式不正确，只支持png,jpg格式的图片"); return;} ???????????????????????????$("#MenuIcon").val(data); ???????????????????????????$("#updatePic").attr("src", data); ???????????????????????????liger.get("COMPANYLICENSE").setValue(data) ???????????????????????????$("#MenuPic").val(""); ???????????????????????????$("#UpdateInfo").text("上传成功！"); ???????????????????????} ???????????????????}); ???????????????} else { ???????????????????$.messager.alert("错误消息", "请选择合法图片！"); ???????????????} ???????????})书写后台管理系统
void ValidatePIC(HttpContext context) ???{ ???????//上传图片 ???????try ???????{ ???????????var requestFile = context.Request.Files["MenuPic"]; ???????????string fname = "/lib/uploads/" + Guid.NewGuid().ToString() + System.IO.Path.GetExtension(requestFile.FileName); ???????????string path = context.Request.MapPath(fname); ???????????requestFile.SaveAs(path); ???????????#region 校验图片 ???????????FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read); ???????????if (fs.Length > 1024 * 1024*4) { ????????????????context.Response.Write("-1"); ????????????????File.Delete(path); //删除文件 ???????????????????return; ???????????} ???????????????BinaryReader reader = new BinaryReader(fs); ???????????????string fileClass; ???????????????byte buffer; ???????????????byte[] b = new byte[2]; ???????????????buffer = reader.ReadByte(); ???????????????b[0] = buffer; ???????????????fileClass = buffer.ToString(); ???????????????buffer = reader.ReadByte(); ???????????????b[1] = buffer; ???????????????fileClass += buffer.ToString(); ???????????????reader.Close(); ???????????????fs.Close(); ???????????#endregion ???????????????if (fileClass == "255216" || fileClass == "7173" || ?fileClass == "13780") ???????????????{ ???????????????????//255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,13780:png ???????????????????????//Response.Write("图片可用"); ????????????????????????//保存到数据库中 ???????????????????????context.Response.Write(fname); ???????????????} ???????????????else ???????????????{ ???????????????????context.Response.Write("-2"); ???????????????????????File.Delete(path); //删除文件 ???????????????????????return; ???????????????} ?????????????????} ???????catch (Exception e) ???????{ ???????????context.Response.Write("-2"); ???????????LogManager.WriteLog("上传图片出错！" + e.Message); ???????} ???}asp.net-html图片的上传
原文地址：http://www.cnblogs.com/kbqLibrary/p/7856282.html