[C#] Hướng dẫn xóa cache trình duyệt WebBrowser trong Csharp

Bài viết hôm nay, mình sẽ tiếp tục hướng dẫn các bạn cách xóa dữ liệu cache, cookie trong trình duyệt WebBrowser control của C#. 

Trong những ứng dụng, khi các bạn đăng nhập để post bài lên các diễn đàn, forum mà có sử dụng control WebBrowser của Visual Studio, nhiều lúc các bạn muốn xóa cache để đăng nhập nhiều tài khoản khác nhau, thì làm thế nào.

Dưới đây mình sẽ chia sẽ cho các bạn cách xóa cache trình duyệt bằng class do Microsoft MSDN cung cấp và đã được chỉnh sửa lại.

Giao diện demo xóa cache trình duyệt bằng C#:

Đầu tiên các bạn tạo một Class có tên DeleteCache.cs với nội dung như sau:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;


public class WebBrowserHelper
{
    #region Definitions/DLL Imports
    /// 
    /// For PInvoke: Contains information about an entry in the Internet cache
    /// 
    [StructLayout(LayoutKind.Explicit)]
    public struct ExemptDeltaOrReserverd
    {
        [FieldOffset(0)]
        public UInt32 dwReserved;
        [FieldOffset(0)]
        public UInt32 dwExemptDelta;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct INTERNET_CACHE_ENTRY_INFOA
    {
        public UInt32 dwStructSize;
        public IntPtr lpszSourceUrlName;
        public IntPtr lpszLocalFileName;
        public UInt32 CacheEntryType;
        public UInt32 dwUseCount;
        public UInt32 dwHitRate;
        public UInt32 dwSizeLow;
        public UInt32 dwSizeHigh;
        public FILETIME LastModifiedTime;
        public FILETIME ExpireTime;
        public FILETIME LastAccessTime;
        public FILETIME LastSyncTime;
        public IntPtr lpHeaderInfo;
        public UInt32 dwHeaderInfoSize;
        public IntPtr lpszFileExtension;
        public ExemptDeltaOrReserverd dwExemptDeltaOrReserved;
    }

    // For PInvoke: Initiates the enumeration of the cache groups in the Internet cache
    [DllImport(@"wininet",
        SetLastError = true,
        CharSet = CharSet.Auto,
        EntryPoint = "FindFirstUrlCacheGroup",
        CallingConvention = CallingConvention.StdCall)]
    public static extern IntPtr FindFirstUrlCacheGroup(
        int dwFlags,
        int dwFilter,
        IntPtr lpSearchCondition,
    int dwSearchCondition,
    ref long lpGroupId,
    IntPtr lpReserved);

    // For PInvoke: Retrieves the next cache group in a cache group enumeration
    [DllImport(@"wininet",
    SetLastError = true,
        CharSet = CharSet.Auto,
    EntryPoint = "FindNextUrlCacheGroup",
        CallingConvention = CallingConvention.StdCall)]
    public static extern bool FindNextUrlCacheGroup(
        IntPtr hFind,
        ref long lpGroupId,
        IntPtr lpReserved);

    // For PInvoke: Releases the specified GROUPID and any associated state in the cache index file
    [DllImport(@"wininet",
        SetLastError = true,
        CharSet = CharSet.Auto,
        EntryPoint = "DeleteUrlCacheGroup",
        CallingConvention = CallingConvention.StdCall)]
    public static extern bool DeleteUrlCacheGroup(
        long GroupId,
        int dwFlags,
        IntPtr lpReserved);

    // For PInvoke: Begins the enumeration of the Internet cache
    [DllImport(@"wininet",
        SetLastError = true,
        CharSet = CharSet.Auto,
        EntryPoint = "FindFirstUrlCacheEntryA",
        CallingConvention = CallingConvention.StdCall)]
    public static extern IntPtr FindFirstUrlCacheEntry(
        [MarshalAs(UnmanagedType.LPTStr)] string lpszUrlSearchPattern,
        IntPtr lpFirstCacheEntryInfo,
        ref int lpdwFirstCacheEntryInfoBufferSize);

    // For PInvoke: Retrieves the next entry in the Internet cache
    [DllImport(@"wininet",
        SetLastError = true,
        CharSet = CharSet.Auto,
        EntryPoint = "FindNextUrlCacheEntryA",
        CallingConvention = CallingConvention.StdCall)]
    public static extern bool FindNextUrlCacheEntry(
        IntPtr hFind,
        IntPtr lpNextCacheEntryInfo,
        ref int lpdwNextCacheEntryInfoBufferSize);

    // For PInvoke: Removes the file that is associated with the source name from the cache, if the file exists
    [DllImport(@"wininet",
        SetLastError = true,
        CharSet = CharSet.Auto,
        EntryPoint = "DeleteUrlCacheEntryA",
        CallingConvention = CallingConvention.StdCall)]
    public static extern bool DeleteUrlCacheEntry(
        IntPtr lpszUrlName);
    #endregion

    /// 
    /// Clears the cache of the web browser
    /// 
    public static void ClearCache()
    {
        // Indicates that all of the cache groups in the user's system should be enumerated
        const int CACHEGROUP_SEARCH_ALL = 0x0;
        // Indicates that all the cache entries that are associated with the cache group
        // should be deleted, unless the entry belongs to another cache group.
        const int CACHEGROUP_FLAG_FLUSHURL_ONDELETE = 0x2;
        const int ERROR_INSUFFICIENT_BUFFER = 0x7A;

        // Delete the groups first.
        // Groups may not always exist on the system.
        // For more information, visit the following Microsoft Web site:
        // http://msdn.microsoft.com/library/?url=/workshop/networking/wininet/overview/cache.asp            
        // By default, a URL does not belong to any group. Therefore, that cache may become
        // empty even when the CacheGroup APIs are not used because the existing URL does not belong to any group.            
        long groupId = 0;
        IntPtr enumHandle = FindFirstUrlCacheGroup(0, CACHEGROUP_SEARCH_ALL, IntPtr.Zero, 0, ref groupId, IntPtr.Zero);
        if (enumHandle != IntPtr.Zero)
        {
            bool more;
            do
            {
                // Delete a particular Cache Group.
                DeleteUrlCacheGroup(groupId, CACHEGROUP_FLAG_FLUSHURL_ONDELETE, IntPtr.Zero);
                more = FindNextUrlCacheGroup(enumHandle, ref groupId, IntPtr.Zero);
            } while (more);
        }

        // Start to delete URLs that do not belong to any group.
        int cacheEntryInfoBufferSizeInitial = 0;
        FindFirstUrlCacheEntry(null, IntPtr.Zero, ref cacheEntryInfoBufferSizeInitial);  // should always fail because buffer is too small
        if (Marshal.GetLastWin32Error() == ERROR_INSUFFICIENT_BUFFER)
        {
            int cacheEntryInfoBufferSize = cacheEntryInfoBufferSizeInitial;
            IntPtr cacheEntryInfoBuffer = Marshal.AllocHGlobal(cacheEntryInfoBufferSize);
            enumHandle = FindFirstUrlCacheEntry(null, cacheEntryInfoBuffer, ref cacheEntryInfoBufferSizeInitial);
            if (enumHandle != IntPtr.Zero)
            {
                bool more;
                do
                {
                    INTERNET_CACHE_ENTRY_INFOA internetCacheEntry = (INTERNET_CACHE_ENTRY_INFOA)Marshal.PtrToStructure(cacheEntryInfoBuffer, typeof(INTERNET_CACHE_ENTRY_INFOA));
                    cacheEntryInfoBufferSizeInitial = cacheEntryInfoBufferSize;
                    DeleteUrlCacheEntry(internetCacheEntry.lpszSourceUrlName);
                    more = FindNextUrlCacheEntry(enumHandle, cacheEntryInfoBuffer, ref cacheEntryInfoBufferSizeInitial);
                    if ( Marshal.GetLastWin32Error() == ERROR_INSUFFICIENT_BUFFER)
                        {
                        cacheEntryInfoBufferSize = cacheEntryInfoBufferSizeInitial;
                        cacheEntryInfoBuffer = Marshal.ReAllocHGlobal(cacheEntryInfoBuffer, (IntPtr)cacheEntryInfoBufferSize);
                        more = FindNextUrlCacheEntry(enumHandle, cacheEntryInfoBuffer, ref cacheEntryInfoBufferSizeInitial);
                    }
                } while (more);
            }
            Marshal.FreeHGlobal(cacheEntryInfoBuffer);
        }
    }
}

Tiếp theo, các bạn chỉ cần gọi hàm DeleteCache cho sự kiện click vào button C# là xong.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;


namespace deleteCacheWebbrowser
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            WebBrowserHelper.ClearCache();


        }
    }
}

HAVE FUN :)