Right-click the root directory of the website, select "add reference" from the shortcut menu, and click "add reference". Switch to "Browse" find the Dll file of the component "Bestcomy. web. controls. upload. dll "(This file can be downloaded at www.aspnetupload.net on the official website. This document will also be available later), click" OK ", and return to the VS working interface, Web. config configuration: Add <section name = "aspnetUploadSettings" type = "System. configuration. nameValueFileSectionHandler, System, Version = 1.0.5000.0, Culture = neutral, PublicKeyToken = b77a5c561934e089 "/> under </configSections>: <aspnetUploadSettin Gs> <add key = "maxRequestLength" value = "2048000" type = "codeph" text = "/codeph"/> <! -- The value here indicates that the maximum size of the file to be uploaded is kb --> </aspnetUploadSettings> I did not add this old one at the beginning and the upload was unsuccessful, value = "2048000" here you can modify the corresponding value. in the <system. web> and </system.