如何清除应用程序承载 WebBrowser 控件时缓存

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文章编号	:	262110
最后修改	:	2007年3月29日
修订	:	3.1

概要

当应用程序承载 WebBrowser 控件, 可能需要以编程方式清除缓存。通过 WebBrowser 控件的接口没有此功能。本文解释如何使用 WinInet API 函数以直接清除缓存。

更多信息

使用 WinInet API FindFirstURLCacheEntry 来找到第一缓存条目和 FindNextUrlCacheEntry 用于列举缓存。使用 DeleteUrlCacheEntry 来删除每个条目。注意 FindFirstUrlCacheGroup DeleteUrlCacheGroup FindNextUrlCacheGroup, 以及正在使用下例中。这些 API 函数以便正确检查作为显示需要防止错误有只成为用 Internet Explorer 5。在下面步骤介绍如何在 VisualBasic 中使用 WinInet API 来清除缓存中所有文件。

1.	新建一个 VisualBasic 标准 EXE 项目。
2.	创建 form 1 下一个命令按钮。
3.	以下代码粘贴到模块是 form 1： Option Explicit Private Declare Function FindFirstUrlCacheGroup Lib "wininet.dll" ( _ ByVal dwFlags As Long, _ ByVal dwFilter As Long, _ ByRef lpSearchCondition As Long, _ ByVal dwSearchCondition As Long, _ ByRef lpGroupId As Date, _ ByRef lpReserved As Long) As Long Private Declare Function FindNextUrlCacheGroup Lib "wininet.dll" ( _ ByVal hFind As Long, _ ByRef lpGroupId As Date, _ ByRef lpReserved As Long) As Long Private Declare Function DeleteUrlCacheGroup Lib "wininet.dll" ( _ ByVal sGroupID As Date, _ ByVal dwFlags As Long, _ ByRef lpReserved As Long) As Long Private Declare Function FindFirstUrlCacheEntry Lib "wininet.dll" Alias "FindFirstUrlCacheEntryA" ( _ ByVal lpszUrlSearchPattern As String, _ ByRef lpFirstCacheEntryInfo As INTERNET_CACHE_ENTRY_INFO, _ ByRef lpdwFirstCacheEntryInfoBufferSize As Long) As Long Private Type INTERNET_CACHE_ENTRY_INFO dwStructSize As Long szRestOfData(1024) As Long End Type Private Declare Function DeleteUrlCacheEntry Lib "wininet.dll" Alias "DeleteUrlCacheEntryA" ( _ ByVal lpszUrlName As Long) As Long Private Declare Function FindNextUrlCacheEntry Lib "wininet.dll" Alias "FindNextUrlCacheEntryA" ( _ ByVal hEnumHandle As Long, _ ByRef lpNextCacheEntryInfo As INTERNET_CACHE_ENTRY_INFO, _ ByRef lpdwNextCacheEntryInfoBufferSize As Long) As Long Private Const CACHGROUP_SEARCH_ALL = &H0 Private Const ERROR_NO_MORE_FILES = 18 Private Const ERROR_NO_MORE_ITEMS = 259 Private Const CACHEGROUP_FLAG_FLUSHURL_ONDELETE = &H2 Private Const BUFFERSIZE = 2048 Private Sub Command1_Click() Dim sGroupID As Date Dim hGroup As Long Dim hFile As Long Dim sEntryInfo As INTERNET_CACHE_ENTRY_INFO Dim iSize As Long On Error Resume Next ' Delete the groups hGroup = FindFirstUrlCacheGroup(0, 0, 0, 0, sGroupID, 0) ' To avoid error using it with IE4 as FindFirstUrlCacheGroup is not implemented If Err.Number <> 453 Then If (hGroup = 0) And (Err.LastDllError <> 2) Then MsgBox "An error occurred enumerating the cache groups" & Err.LastDllError Exit Sub End If Else Err.Clear End If If (hGroup <> 0) Then 'we succeeded in finding the first cache group.. enumerate and 'delete Do If (0 = DeleteUrlCacheGroup(sGroupID, CACHEGROUP_FLAG_FLUSHURL_ONDELETE, 0)) Then ' To avoid error using it with IE4 as FindFirstUrlCacheGroup is not implemented If Err.Number <> 453 Then MsgBox "Error deleting cache group " & Err.LastDllError Exit Sub Else Err.Clear End If End If iSize = BUFFERSIZE If (0 = FindNextUrlCacheGroup(hGroup, sGroupID, iSize)) And (Err.LastDllError <> 2) Then MsgBox "Error finding next url cache group! - " & Err.LastDllError End If Loop Until Err.LastDllError = 2 End If ' Delete the files sEntryInfo.dwStructSize = 80 iSize = BUFFERSIZE hFile = FindFirstUrlCacheEntry(0, sEntryInfo, iSize) If (hFile = 0) Then If (Err.LastDllError = ERROR_NO_MORE_ITEMS) Then GoTo done End If MsgBox "ERROR: FindFirstUrlCacheEntry - " & Err.LastDllError Exit Sub End If Do If (0 = DeleteUrlCacheEntry(sEntryInfo.szRestOfData(0))) _ And (Err.LastDllError <> 2) Then Err.Clear End If iSize = BUFFERSIZE If (0 = FindNextUrlCacheEntry(hFile, sEntryInfo, iSize)) And (Err.LastDllError <> ERROR_NO_MORE_ITEMS) Then MsgBox "Error: Unable to find the next cache entry - " & Err.LastDllError Exit Sub End If Loop Until Err.LastDllError = ERROR_NO_MORE_ITEMS done: MsgBox "cache cleared" Command1.Enabled = True End Sub
4.	运行项目并单击 Command 。计算机中缓存将被清除。