[英]Modify the content of the home page programmatically in SharePoint 2010
[英]Modify file content programmatically
我必須使用 C# 以編程方式修改文件中的文本。執行此操作並避免重寫整個文件內容的最佳方法是什么。 我只想編輯一些單詞並保存。
正如其他人所說,您可以輕松地 append 到現有文件。 在文件中間插入數據需要您寫出文件的其余部分。 沒有辦法只移動文件中的所有內容。 如果您想就地覆蓋單個字節,您可以打開一個FileStream 。 然后,您使用“Seek”到 go 到您要覆蓋的特定字節,並使用 Write 或 WriteByte 將現有數據覆蓋為新數據。
您可以使用 StreamWriter 和 AppendText 輕松地 append 到現有文件。
如果你想做更嚴重的修改,那么我認為你必須使用 StreamReader 將文件的內容讀入 C# 中的 memory,以編程方式修改 stream 的內容,然后用流的內容重寫文件。
我認為無論如何都是如此。
如果您的目標是 windows,則可以使用 winapi CreateFile、ReadFile、WriteFile 等。 您可以輕松地寫入文件中的任何位置並寫入任意數量的數據。 您不必重寫該文件。 這甚至不需要不安全的代碼。 我限制了函數的功能(沒有異步或古怪的文件映射)只是為了快速完成這項工作,但它可以毫無問題地讀寫文件。 為了讓這個例子工作,制作一個 100 字節左右的小文本文件,並確保它在 exe 的位置。 此代碼的一小部分來自 MSDN 網站。 不過,我已經對其進行了重大修改。
using System;
using Microsoft.Win32.SafeHandles;
using System.Runtime.InteropServices;
using System.ComponentModel;
using System.Windows.Forms;
using Path = System.IO.Path;
class Program {
static void Main() {
string sTestFile = Path.Combine(Path.GetDirectoryName(
Application.ExecutablePath), "Test.txt");
// test reading a file
WinApiFile File = new WinApiFile(sTestFile,
WinApiFile.DesiredAccess.GENERIC_READ);
byte[] aBuffer = new byte[1000];
uint cbRead = File.Read(aBuffer, 1000);
File.Close();
// Test writing the file
File.Open(WinApiFile.DesiredAccess.GENERIC_WRITE);
// write the time to a 10 byte offset in the file
// conver the date time to byte array
int i = 0;
foreach (var ch in DateTime.Now.ToString())
aBuffer[i++] = (byte)ch;
// now write it out
File.MoveFilePointer(10); // 10 byte offset
File.Write(aBuffer, (uint)i); // write the time
File.Dispose();
}
}
public class WinApiFile : IDisposable {
/* ---------------------------------------------------------
* private members
* ------------------------------------------------------ */
private SafeFileHandle _hFile = null;
private string _sFileName = "";
private bool _fDisposed;
/* ---------------------------------------------------------
* properties
* ------------------------------------------------------ */
public bool IsOpen { get { return (_hFile != null); } }
public SafeFileHandle Handle { get { return _hFile; } }
public string FileName {
get { return _sFileName; }
set {
_sFileName = (value ?? "").Trim();
if (_sFileName.Length == 0)
CloseHandle(_hFile);
}
}
public int FileLength {
get {
return (_hFile != null) ? (int)GetFileSize(_hFile,
IntPtr.Zero) : 0;
}
set {
if (_hFile == null)
return;
MoveFilePointer(value, MoveMethod.FILE_BEGIN);
if (!SetEndOfFile(_hFile))
ThrowLastWin32Err();
}
}
/* ---------------------------------------------------------
* Constructors
* ------------------------------------------------------ */
public WinApiFile(string sFileName,
DesiredAccess fDesiredAccess) {
FileName = sFileName;
Open(fDesiredAccess);
}
public WinApiFile(string sFileName,
DesiredAccess fDesiredAccess,
CreationDisposition fCreationDisposition) {
FileName = sFileName;
Open(fDesiredAccess, fCreationDisposition);
}
/* ---------------------------------------------------------
* Open/Close
* ------------------------------------------------------ */
public void Open(
DesiredAccess fDesiredAccess) {
Open(fDesiredAccess, CreationDisposition.OPEN_EXISTING);
}
public void Open(
DesiredAccess fDesiredAccess,
CreationDisposition fCreationDisposition) {
ShareMode fShareMode;
if (fDesiredAccess == DesiredAccess.GENERIC_READ) {
fShareMode = ShareMode.FILE_SHARE_READ;
} else {
fShareMode = ShareMode.FILE_SHARE_NONE;
}
Open(fDesiredAccess, fShareMode, fCreationDisposition, 0);
}
public void Open(
DesiredAccess fDesiredAccess,
ShareMode fShareMode,
CreationDisposition fCreationDisposition,
FlagsAndAttributes fFlagsAndAttributes) {
if (_sFileName.Length == 0)
throw new ArgumentNullException("FileName");
_hFile = CreateFile(_sFileName, fDesiredAccess, fShareMode,
IntPtr.Zero, fCreationDisposition, fFlagsAndAttributes,
IntPtr.Zero);
if (_hFile.IsInvalid) {
_hFile = null;
ThrowLastWin32Err();
}
_fDisposed = false;
}
public void Close() {
if (_hFile == null)
return;
_hFile.Close();
_hFile = null;
_fDisposed = true;
}
/* ---------------------------------------------------------
* Move file pointer
* ------------------------------------------------------ */
public void MoveFilePointer(int cbToMove) {
MoveFilePointer(cbToMove, MoveMethod.FILE_CURRENT);
}
public void MoveFilePointer(int cbToMove,
MoveMethod fMoveMethod) {
if (_hFile != null)
if (SetFilePointer(_hFile, cbToMove, IntPtr.Zero,
fMoveMethod) == INVALID_SET_FILE_POINTER)
ThrowLastWin32Err();
}
public int FilePointer {
get {
return (_hFile != null) ? (int)SetFilePointer(_hFile, 0,
IntPtr.Zero, MoveMethod.FILE_CURRENT) : 0;
}
set {
MoveFilePointer(value);
}
}
/* ---------------------------------------------------------
* Read and Write
* ------------------------------------------------------ */
public uint Read(byte[] buffer, uint cbToRead) {
// returns bytes read
uint cbThatWereRead = 0;
if (!ReadFile(_hFile, buffer, cbToRead,
ref cbThatWereRead, IntPtr.Zero))
ThrowLastWin32Err();
return cbThatWereRead;
}
public uint Write(byte[] buffer, uint cbToWrite) {
// returns bytes read
uint cbThatWereWritten = 0;
if (!WriteFile(_hFile, buffer, cbToWrite,
ref cbThatWereWritten, IntPtr.Zero))
ThrowLastWin32Err();
return cbThatWereWritten;
}
/* ---------------------------------------------------------
* IDisposable Interface
* ------------------------------------------------------ */
public void Dispose() {
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool fDisposing) {
if (!_fDisposed) {
if (fDisposing) {
if (_hFile != null)
_hFile.Dispose();
_fDisposed = true;
}
}
}
~WinApiFile() {
Dispose(false);
}
/* ---------------------------------------------------------
* WINAPI STUFF
* ------------------------------------------------------ */
private void ThrowLastWin32Err() {
Marshal.ThrowExceptionForHR(
Marshal.GetHRForLastWin32Error());
}
[Flags]
public enum DesiredAccess : uint {
GENERIC_READ = 0x80000000,
GENERIC_WRITE = 0x40000000
}
[Flags]
public enum ShareMode : uint {
FILE_SHARE_NONE = 0x0,
FILE_SHARE_READ = 0x1,
FILE_SHARE_WRITE = 0x2,
FILE_SHARE_DELETE = 0x4,
}
public enum MoveMethod : uint {
FILE_BEGIN = 0,
FILE_CURRENT = 1,
FILE_END = 2
}
public enum CreationDisposition : uint {
CREATE_NEW = 1,
CREATE_ALWAYS = 2,
OPEN_EXISTING = 3,
OPEN_ALWAYS = 4,
TRUNCATE_EXSTING = 5
}
[Flags]
public enum FlagsAndAttributes : uint {
FILE_ATTRIBUTES_ARCHIVE = 0x20,
FILE_ATTRIBUTE_HIDDEN = 0x2,
FILE_ATTRIBUTE_NORMAL = 0x80,
FILE_ATTRIBUTE_OFFLINE = 0x1000,
FILE_ATTRIBUTE_READONLY = 0x1,
FILE_ATTRIBUTE_SYSTEM = 0x4,
FILE_ATTRIBUTE_TEMPORARY = 0x100,
FILE_FLAG_WRITE_THROUGH = 0x80000000,
FILE_FLAG_OVERLAPPED = 0x40000000,
FILE_FLAG_NO_BUFFERING = 0x20000000,
FILE_FLAG_RANDOM_ACCESS = 0x10000000,
FILE_FLAG_SEQUENTIAL_SCAN = 0x8000000,
FILE_FLAG_DELETE_ON = 0x4000000,
FILE_FLAG_POSIX_SEMANTICS = 0x1000000,
FILE_FLAG_OPEN_REPARSE_POINT = 0x200000,
FILE_FLAG_OPEN_NO_CALL = 0x100000
}
public const uint INVALID_HANDLE_VALUE = 0xFFFFFFFF;
public const uint INVALID_SET_FILE_POINTER = 0xFFFFFFFF;
// Use interop to call the CreateFile function.
// For more information about CreateFile,
// see the unmanaged MSDN reference library.
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern SafeFileHandle CreateFile(
string lpFileName,
DesiredAccess dwDesiredAccess,
ShareMode dwShareMode,
IntPtr lpSecurityAttributes,
CreationDisposition dwCreationDisposition,
FlagsAndAttributes dwFlagsAndAttributes,
IntPtr hTemplateFile);
[DllImport("kernel32", SetLastError = true)]
internal static extern Int32 CloseHandle(
SafeFileHandle hObject);
[DllImport("kernel32", SetLastError = true)]
internal static extern bool ReadFile(
SafeFileHandle hFile,
Byte[] aBuffer,
UInt32 cbToRead,
ref UInt32 cbThatWereRead,
IntPtr pOverlapped);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern bool WriteFile(
SafeFileHandle hFile,
Byte[] aBuffer,
UInt32 cbToWrite,
ref UInt32 cbThatWereWritten,
IntPtr pOverlapped);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern UInt32 SetFilePointer(
SafeFileHandle hFile,
Int32 cbDistanceToMove,
IntPtr pDistanceToMoveHigh,
MoveMethod fMoveMethod);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern bool SetEndOfFile(
SafeFileHandle hFile);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern UInt32 GetFileSize(
SafeFileHandle hFile,
IntPtr pFileSizeHigh);
}
當您打開文件進行寫入時,只有兩種可能的結果。 要么打開它進行附加,這將允許您只在末尾寫入,要么打開它進行正常寫入,在這種情況下,您將從文件的開頭寫入。 沒有“在中點打開,寫入然后根據插入長度移動剩余內容”。
某些 API 可能會允許這樣的修改,但在幕后,它們只允許您執行這兩個基本操作。 你不應該太擔心重寫整個文件,但是,除非你的文件很大並且你的硬盤驅動器非常慢,否則它並不是一個糟糕的操作。 相反,您應該更擔心這樣做的次數。
讀入文件並修改它然后再次讀出它可能更簡單。
為了真正高效(即不是為每個操作讀取/寫入整個文件),您需要做一些內務處理以跟蹤有關文件的元數據,然后進行二進制編輯。
您仍然需要管理文件增長和需要附加的情況等。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.