关于异步下载，使用 XMLHttp也好，WINHttp也好，都有成功案例。这里介绍另一种技术：使用 .NET FrameWork 的 System.Net.WebClient 实现下载。
这里借助的第三方为开源的 wwDotNetBridge。需要中文版详细文档的可以直接联系本文作者/译者，收费提供。
VFP可以调用的.NET--加菲猫注
示例1：同步下载：
代码语言：javascript复制
CLEAR
DO wwDotNetBridge
Public loBridge as wwDotNetBridge
loBridge = CreateObject("wwDotNetBridge","V4")
loClient = loBridge.CreateInstance("System.Net.WebClient")
lcUrl = "下载的 URL 地址"
lcLocalPath = "带有完整路径的文件名"
loClient.DownloadFile(lcUrl, lcLocalPath)示例2：“伪”异步下载
代码语言：javascript复制CLEAR
DO wwDotNetBridge
Public loBridge as wwDotNetBridge
loBridge = CreateObject("wwDotNetBridge","V4)
loClient = loBridge.CreateInstance("System.Net.WebClient")
PUBLIC loCallback
loCallback = CREATEOBJECT("MyCallback")
lcUrl = "下载的 URL 地址"
lcLocalPath = "带有完整路径的文件名"
loBridge.InvokeMethodAsync(loCallback,loClient,"DownloadFile",lcUrl, lcLocalPath)
DOEVENTS
Read EVENTS
loClient.Dispose()
DEFINE CLASS MyCallback as AsyncCallbackEvents
FUNCTION OnCompleted(lvResult,lcMethod)
? "Success: " lcMethod,lvResult
Clear Events
ENDFUNC
FUNCTION OnError(lcMessage,loException,lcMethod)
? "Error: " lcMethod,lcMessage
Clear Events
ENDFUNC
ENDDEFINE示例3：异步下载
代码语言：javascript复制CLEAR
DO wwDotNetBridge
Public loBridge as wwDotNetBridge
loBridge = CreateObject("wwDotNetBridge","V4")
loClient = loBridge.CreateInstance("System.Net.WebClient")
loHandler = CREATEOBJECT("DownloadEventHandler")
loSubscription = loBridge.SubscribeToEvents(loClient, loHandler)
lcUrl = "下载的 URL 地址"
loUrl = loBridge.CreateInstance("System.Uri", lcUrl)
lcLocalPath = "带有完整路径的文件名"
loClient.DownloadFileAsync(loUrl, lcLocalPath)
DOEVENTS
Read EVENTS
loSubscription.Unsubscribe()
loClient.Dispose()
DEFINE CLASS DownloadEventHandler as Custom
FUNCTION OnDownloadProgressChanged(sender, e)
? "下载进度：" TRANS(loBridge.GetProperty(e,"ProgressPercentage")) "%"
ENDFUNC
FUNCTION OnDownloadFileCompleted(sender, e)
? "下载成功"
Clear Events
ENDFUNC
ENDDEFINE
