看看效果：
在专案中，创建aspx页面，拉上FileUpload控件一个Image，将用来预览上传时的图片。
View Code <% @ Page Language = " C# " AutoEventWireup = " true " CodeFile = " Default2.aspx.cs " Inherits = " Default2 " %> <! DOCTYPE html > < html xmlns ="http://www.w3.org/1999/xhtml" > < head runat ="server" > < title ></ title > </ head > < body > < form id ="form1" runat ="server" > < div > < table > < tr > < td style ="vertical-align: top; width: 10%;" > < fieldset > < legend >选择图片 </ legend > < asp:FileUpload ID ="FileUpload1" runat ="server" /> </ fieldset > </ td > < td style ="vertical-align: top; width: 90%;" > < fieldset > < legend >预览 </ legend > < asp:Image ID ="Image1" runat ="server" Visible ="false" /> </ fieldset > </ td > </ tr > </ table > </ div > </ form > </ body > </ html >
在Page_Init事件中，为FileUpload控件，注册onchange客户端事件。
View Code protected void Page_Init( object sender, EventArgs e) { this.FileUpload1.Attributes.Add( " onchange ", Page.ClientScript.GetPostBackEventReference( this.FileUpload1, " onchange ")); }
接下来，Insus.NET一个axd处理文档，其实ImageProcessFactory.cs只是一个普能的类别，只实作了IHttpHandler接口。
ImageProcessFactory.cs using System; using System.Collections.Generic; using System.Drawing; using System.Drawing.Drawing2D; using System.Drawing.Imaging; using System.IO; using System.Linq; using System.Web; using System.Web.SessionState; /// <summary> /// Summary description for ImageProcessFactory /// </summary> namespace Insus.NET { public class ImageProcessFactory : IHttpHandler,IRequiresSessionState { public ImageProcessFactory() { // // TODO: Add constructor logic here // } public void ProcessRequest(HttpContext context) { // Checking whether the UploadBytes session variable have anything else not doing anything if ((context.Session[ " UploadBytes "]) != null) { byte[] buffer = ( byte[])(context.Session[ " UploadBytes "]); context.Response.BinaryWrite(buffer); } } public bool IsReusable { get { return false; } } } }
为能能应到axd文档，需要在Web.Config中配置一下。
View Code < configuration > < system.web > < httpHandlers > < add verb ="*" path ="PreviewImage.axd" type ="Insus.NET.ImageProcessFactory" /> </ httpHandlers > </ system.web > </ configuration >
Ok，我们回到aspx.cs页面中，要在page_Load中，怎监控FileUpload控件是否有值变化：
View Code protected void Page_Load( object sender, EventArgs e) { if (IsPostBack) { var ctrl = Request.Params[Page.postEventSourceID]; var args = Request.Params[Page.postEventArgumentID]; OnchangeHandle(ctrl, args); } }
在Page_Load中有一个方法OnchangeHandle(xxx,xxx):
View Code
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