在 Visual C++ 中執行基本檔案 I/O

發行項
03/24/2024

本文說明如何在 Microsoft Visual C++ 或 Visual C++ .NET 中執行基本檔案輸入/輸出 (I/O) 作業。

原始產品版本： Visual C++
原始 KB 編號： 307398

摘要

如果您不熟悉 .NET Framework，您會發現 .NET Framework 中檔案作業的物件模型與許多 Visual Studio 開發人員常用的類似FileSystemObject。

若要簡化轉換，請參閱如何搭配 Visual Basic 使用 FileSystemObject。
如需本文的 Visual C# .NET 版本，請參閱如何在 Visual C# 中執行基本檔案 I/O。

本文參考下列 .NET Framework 類別庫命名空間：

System::ComponentModel
System::Windows::Forms
System::Drawing

您仍然可以在 .NET Framework 中使用 FileSystemObject 。 FileSystemObject因為是元件物件模型 (COM) 元件，所以 .NET Framework 需要透過 Interop 層存取物件。如果您想要使用元件，.NET Framework 會為您產生包裝函式。不過，類別File、FileInfo類別、、DirectoryDirectoryInfo類別，以及 .NET Framework 中的其他相關類別，會提供不含 FileSystemObjectInterop 層額外負荷的功能。

示範的檔案 I/O 作業

本文中的範例說明基本檔案 I/O 作業。逐步範例一節說明如何建立範例程式，示範下列六個檔案 I/O 作業：

讀取文字檔
撰寫文字檔
檢視檔案資訊
列出磁碟驅動器
列出子資料夾
列出檔案

讀取文字檔

下列範例程式代碼會使用 StreamReader 類別來讀取文字檔。檔案的內容會新增至 ListBox 控制件。如果 try...catch 檔案是空的，則會使用區塊來警示程式。有許多方法可以判斷何時到達檔尾;這個範例會使用 Peek 方法來檢查下一行，然後再讀取它。

listBox1->Items->Clear();
try
{
    String* textFile = String::Concat(windir, (S"\\mytest.txt"));
    StreamReader *reader=new  StreamReader(textFile);
    do
    {
        listBox1->Items->Add(reader->ReadLine());
    } while(reader->Peek() != -1);
}

catch (System::Exception *e)
{
    listBox1->Items->Add(e);
}

在 Visual C++ 中，您必須將 Common Language Runtime 支援編譯程式選項新增 (/clr：oldSyntax) ，才能成功將先前的程式代碼範例編譯為 Managed C++。若要新增 Common Language Runtime 支援編譯程式選項，請遵循下列步驟：

按兩下 [專案]，然後按兩下 [<ProjectName> 屬性]。

注意事項

<ProjectName> 是專案名稱的佔位元。
展開 [ 組態屬性]，然後按兩下 [ 一般]。
在右窗格中，按兩下以選取 Common Language Runtime 支援、Common Language Runtime 支援項目設定中的舊語法 (/clr：oldSyntax) 。
在 [撥號對應表 (電話內容)] 方塊中，按一下 [瀏覽] 以尋找使用者的撥號對應表。

撰寫文字檔

此範例程式代碼會使用 StreamWriter 類別來建立和寫入檔案。如果您有現有的檔案，可以用相同方式開啟它。

StreamWriter* pwriter = new StreamWriter(S"c:\\KBTest.txt");
pwriter->WriteLine(S"File created using StreamWriter class.");
pwriter->Close();
listBox1->Items->Clear();
String *filew = new String(S"File Written to C:\\KBTest.txt");
listBox1->Items->Add(filew);

檢視檔案資訊

此範例程式代碼會使用 FileInfo 類別來存取檔案的屬性。此範例中會使用 Notepad.exe。屬性會出現在 ListBox 控制件中。

listBox1->Items->Clear();
String* testfile = String::Concat(windir, (S"\\notepad.exe"));
FileInfo *pFileProps =new FileInfo(testfile);

listBox1->Items->Add(String::Concat(S"File Name = ", (pFileProps->get_FullName())));
listBox1->Items->Add(String::Concat(S"Creation Time = ", (pFileProps->get_CreationTime()).ToString()));
listBox1->Items->Add(String::Concat(S"Last Access Time = " ,(pFileProps->get_LastAccessTime()).ToString()));
listBox1->Items->Add(String::Concat(S"Last Write Time = ", (pFileProps->get_LastWriteTime()).ToString()));
listBox1->Items->Add(String::Concat(S"Size = ", (pFileProps->get_Length()).ToString()));

列出磁碟驅動器

此範例程式代碼會使用 Directory 和 Drive 類別來列出系統上的邏輯磁碟驅動器。在此範例中，結果會出現在 ListBox 控制件中。

listBox1->Items->Clear();
String* drives[] = Directory::GetLogicalDrives();
int numDrives = drives->get_Length();
for (int i=0; i<numDrives; i++)
{
    listBox1->Items->Add(drives[i]);
}

列出子資料夾

此範例程式代碼會使用 GetDirectories 類別的 Directory 方法來取得資料夾清單。

listBox1->Items->Clear();
String* dirs[] = Directory::GetDirectories(windir);
int numDirs = dirs->get_Length();
for (int i=0; i<numDirs; i++)
{
    listBox1->Items->Add(dirs[i]);
}

列出檔案

此範例程式代碼會使用 GetFiles 類別的 Directory 方法來取得檔案清單。

listBox1->Items->Clear();
String* files[]= Directory::GetFiles(this->windir);
int numFiles = files->get_Length();
for (int i=0; i<numFiles; i++)
{
    listBox1->Items->Add(files[i]);
}

當使用者取得檔案的存取權時，可能會發生許多錯誤。檔案可能不存在、檔案可能正在使用中，或使用者可能沒有他們嘗試存取之資料夾檔案的許可權。當您撰寫程式代碼來處理可能產生的例外狀況時，請考慮這些可能性。

逐步範例

啟動 Visual Studio .NET。
在 [檔案] 功能表中，按一下 [新增]，然後按一下 [專案]。
在 [項目類型] 底下，按兩下 [Visual C++ 專案]。在 [範本] 區段下，按兩下 [Windows Forms 應用程式] (.NET) ] 。
在 [名稱] 方塊中輸入KB307398，在 [位置] 方塊中輸入 C:\ ，然後按兩下 [確定]。
在 [設計] 檢視中開啟 Form1 窗體，然後按 F4 開啟 [ 屬性] 視窗。
在 [ 屬性] 視窗中，展開 [ 大小 ] 資料夾。在 [ 寬度] 方 塊中，輸入 700。在 [ 高度] 方 塊中，輸入 320。
將一個 ListBox 控制件和六個按鈕控制項新增至 Form1。

注意事項

若要檢視工具箱，請單擊 [檢視] 功能表上的 [工具箱]。

在 [ 屬性] 視窗中，變更這些控件 的 [位置]、[ 名稱]、[ 大小]、 [TabIndex] 和 [文字 ] 屬性，如下所示：

控制項 ID	位置	名稱	大小	TabIndex	Text
button1	500, 32	button1	112, 23	1	讀取文字檔
button2	500, 64	button2	112, 23	2	寫入文字檔
button3	500, 96	button3	112, 23	3	檢視檔案資訊
button4	500, 128	button4	112, 23	4	列出磁碟驅動器
button5	500, 160	button5	112, 23	5	列出子資料夾
button6	500, 192	button6	112, 23	6	列出檔案
listBox1	24, 24	listBox1	450, 200	0	listBox1

開啟 Form1.h 檔案。在類別宣告中 Form1 ，使用下列程式代碼宣告一個私 String 用變數：
```
private:
String *windir;
```

在 Form1 類別建構函式中，新增下列程序代碼：

windir = System::Environment::GetEnvironmentVariable("windir");

若要執行檔案輸入輸出作業，請新增 System::IO 命名空間。

按 SHIFT+F7 以在設計檢視中開啟 Form1 。按兩下 [ 讀取文字檔案] 按鈕，然後貼上下列程式代碼：

// How to read a text file:
// Use try...catch to deal with a 0 byte file or a non-existant file.
listBox1->Items->Clear();

try
{
    String* textFile = String::Concat(windir, (S"\\mytest.txt"));
    StreamReader *reader=new  StreamReader(textFile);
    do
    {
        listBox1->Items->Add(reader->ReadLine());
    } while(reader->Peek() != -1);
}
catch(FileNotFoundException *ex)
{
    listBox1->Items->Add(ex);
}  

catch (System::Exception *e)
{
    listBox1->Items->Add(e);
}

在 [Form1 設計] 檢視中，按兩下 [ 寫入文字檔] 按鈕，然後貼上下列程式代碼：

// This demonstrates how to create and to write to a text file.
StreamWriter* pwriter = new StreamWriter(S"c:\\KBTest.txt");
pwriter->WriteLine(S"The file was created by using the StreamWriter class.");
pwriter->Close();
listBox1->Items->Clear();
String *filew = new String(S"File written to C:\\KBTest.txt");
listBox1->Items->Add(filew);

在 [Form1 設計] 檢視中，按兩下 [ 檢視檔案資訊 ] 按鈕，然後在方法中貼上下列程式代碼：

// This code retrieves file properties. The example uses Notepad.exe.
listBox1->Items->Clear();
String* testfile = String::Concat(windir, (S"\\notepad.exe"));
FileInfo *pFileProps =new FileInfo(testfile);

listBox1->Items->Add(String::Concat(S"File Name = ", (pFileProps->get_FullName())));
listBox1->Items->Add(String::Concat(S"Creation Time = ", (pFileProps->get_CreationTime()).ToString()));
listBox1->Items->Add(String::Concat(S"Last Access Time = " ,(pFileProps->get_LastAccessTime()).ToString()));
listBox1->Items->Add(String::Concat(S"Last Write Time = ", (pFileProps->get_LastWriteTime()).ToString()));
listBox1->Items->Add(String::Concat(S"Size = ", (pFileProps->get_Length()).ToString()));

在 [Form1 設計] 檢視中，按兩下 [清單磁碟驅動器] 按鈕，然後貼上下列程式代碼：

// This demonstrates how to obtain a list of disk drives.
listBox1->Items->Clear();
String* drives[] = Directory::GetLogicalDrives();
int numDrives = drives->get_Length();
for (int i=0; i<numDrives; i++)
{
    listBox1->Items->Add(drives[i]);
}

在 [Form1 設計] 檢視中，按兩下 [列出子資料夾] 按鈕，然後貼上下列程式代碼：

// This code obtains a list of folders. This example uses the Windows folder.
listBox1->Items->Clear();
String* dirs[] = Directory::GetDirectories(windir);
int numDirs = dirs->get_Length();
for (int i=0; i<numDirs; i++)
{
    listBox1->Items->Add(dirs[i]);
}

在 [Form1 設計] 檢視中，按兩下 [列出檔案] 按鈕，然後貼上下列程式代碼：

// This code obtains a list of files. This example uses the Windows folder.
listBox1->Items->Clear();
String* files[]= Directory::GetFiles(this->windir);
int numFiles = files->get_Length();
for (int i=0; i<numFiles; i++)
{
    listBox1->Items->Add(files[i]);
}

若要建置然後執行程式，請按 CTRL+F5。

完整程式代碼範例

//Form1.h
#pragma once

namespace KB307398
{
    using namespace System;
    using namespace System::IO;
    using namespace System::ComponentModel;
    using namespace System::Collections;
    using namespace System::Windows::Forms;
    using namespace System::Data;
    using namespace System::Drawing;

    /// <summary>
    /// Summary for Form1
    /// WARNING: If you change the name of this class, you will need to change the
    ///          'Resource File Name' property for the managed resource compiler tool
    ///          associated with all .resx files this class depends on.  Otherwise,
    ///          the designers will not be able to interact properly with localized
    ///          resources associated with this form.
    /// </summary>
    public __gc class Form1 : public System::Windows::Forms::Form
    {
        private:
        String *windir;
        public:
        Form1(void)
        {
            windir = System::Environment::GetEnvironmentVariable("windir");
            InitializeComponent();
        }

        protected:
        void Dispose(Boolean disposing)
        {
            if (disposing && components)
            {
            components->Dispose();
            }
            __super::Dispose(disposing);
        }
        private: System::Windows::Forms::Button *  button1;
        private: System::Windows::Forms::Button *  button2;
        private: System::Windows::Forms::Button *  button3;
        private: System::Windows::Forms::Button *  button4;
        private: System::Windows::Forms::Button *  button5;
        private: System::Windows::Forms::Button *  button6;
        private: System::Windows::Forms::ListBox *  listBox1;

        private:
        /// <summary>
        /// Required designer variable.
        /// </summary>
        System::ComponentModel::Container * components;

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        void InitializeComponent(void)
        {
            this->button1 = new System::Windows::Forms::Button();
            this->button2 = new System::Windows::Forms::Button();
            this->button3 = new System::Windows::Forms::Button();
            this->button4 = new System::Windows::Forms::Button();
            this->button5 = new System::Windows::Forms::Button();
            this->button6 = new System::Windows::Forms::Button();
            this->listBox1 = new System::Windows::Forms::ListBox();
            this->SuspendLayout();
            // button1
            this->button1->Location = System::Drawing::Point(500, 32);
            this->button1->Name = S"button1";
            this->button1->Size = System::Drawing::Size(112, 23);
            this->button1->TabIndex = 1;
            this->button1->Text = S"Read Text File";
            this->button1->Click += new System::EventHandler(this, button1_Click);
            // button2
            this->button2->Location = System::Drawing::Point(500, 64);
            this->button2->Name = S"button2";
            this->button2->Size = System::Drawing::Size(112, 23);
            this->button2->TabIndex = 2;
            this->button2->Text = S"Write Text File";
            this->button2->Click += new System::EventHandler(this, button2_Click);
            // button3
            this->button3->Location = System::Drawing::Point(500, 96);
            this->button3->Name = S"button3";
            this->button3->Size = System::Drawing::Size(112, 23);
            this->button3->TabIndex = 3;
            this->button3->Text = S"View File Information";
            this->button3->Click += new System::EventHandler(this, button3_Click);
            // button4
            this->button4->Location = System::Drawing::Point(500, 128);
            this->button4->Name = S"button4";
            this->button4->Size = System::Drawing::Size(112, 23);
            this->button4->TabIndex = 4;
            this->button4->Text = S"List Drives";
            this->button4->Click += new System::EventHandler(this, button4_Click);
            // button5
            this->button5->Location = System::Drawing::Point(500, 160);
            this->button5->Name = S"button5";
            this->button5->Size = System::Drawing::Size(112, 23);
            this->button5->TabIndex = 5;
            this->button5->Text = S"List Subfolders";
            this->button5->Click += new System::EventHandler(this, button5_Click);
            // button6
            this->button6->Location = System::Drawing::Point(500, 188);
            this->button6->Name = S"button6";
            this->button6->Size = System::Drawing::Size(112, 23);
            this->button6->TabIndex = 6;
            this->button6->Text = S"List Files";
            this->button6->Click += new System::EventHandler(this, button6_Click);
            // listBox1
            this->listBox1->Location = System::Drawing::Point(24, 24);
            this->listBox1->Name = S"listBox1";
            this->listBox1->Size = System::Drawing::Size(450, 199);
            this->listBox1->TabIndex = 0;
            // Form1
            this->AutoScaleBaseSize = System::Drawing::Size(5, 13);
            this->ClientSize = System::Drawing::Size(692, 293);
            this->Controls->Add(this->listBox1);
            this->Controls->Add(this->button6);
            this->Controls->Add(this->button5);
            this->Controls->Add(this->button4);
            this->Controls->Add(this->button3);
            this->Controls->Add(this->button2);
            this->Controls->Add(this->button1);
            this->Name = S"Form1";
            this->Text = S"Form1";
            this->ResumeLayout(false);
        }
        private: System::Void button1_Click(System::Object *  sender, System::EventArgs *  e)
        {
            // This code shows how to read a text file.
            // The try...catch code is to deal with a 0 byte file or a non-existant file.
            listBox1->Items->Clear();

            try
            {
                String* textFile = String::Concat(windir, (S"\\mytest.txt"));
                StreamReader *reader=new  StreamReader(textFile);
                do
                {
                    listBox1->Items->Add(reader->ReadLine());
                }
                while(reader->Peek() != -1);
            }
            catch(FileNotFoundException *ex)
            {
                listBox1->Items->Add(ex);
            }

            catch (System::Exception *e)
            {
                listBox1->Items->Add(e);
            }
        }

        private: System::Void button2_Click(System::Object *  sender, System::EventArgs *  e)
        {
            // This code demonstrates how to create and to write to a text file.
            StreamWriter* pwriter = new StreamWriter(S"c:\\KBTest.txt");
            pwriter->WriteLine(S"The file was created by using the StreamWriter class.");
            pwriter->Close();
            listBox1->Items->Clear();
            String *filew = new String(S"The file was written to C:\\KBTest.txt");
            listBox1->Items->Add(filew);
        }

        private: System::Void button3_Click(System::Object *  sender, System::EventArgs *  e)
         {
            // This code retrieves file properties. This example uses Notepad.exe.
            listBox1->Items->Clear();
            String* testfile = String::Concat(windir, (S"\\notepad.exe"));
            FileInfo *pFileProps  =new FileInfo(testfile);

            listBox1->Items->Add(String::Concat(S"File Name = ", (pFileProps->get_FullName() )) );
            listBox1->Items->Add(String::Concat(S"Creation Time = ", (pFileProps->get_CreationTime() ).ToString()) );
            listBox1->Items->Add(String::Concat(S"Last Access Time = "  ,(pFileProps->get_LastAccessTime() ).ToString()) );
            listBox1->Items->Add(String::Concat(S"Last Write Time = ", (pFileProps->get_LastWriteTime() ).ToString()) );
            listBox1->Items->Add(String::Concat(S"Size = ", (pFileProps->get_Length() ).ToString()) );
        }

        private: System::Void button4_Click(System::Object *  sender, System::EventArgs *  e)
        {
            // The code demonstrates how to obtain a list of disk drives.
            listBox1->Items->Clear();
            String* drives[] = Directory::GetLogicalDrives();
            int numDrives = drives->get_Length();
            for (int i=0; i<numDrives; i++)
            {
                listBox1->Items->Add(drives[i]);
            }
        }

        private: System::Void button5_Click(System::Object *  sender, System::EventArgs *  e)
        {
            // This code obtains a list of folders. This example uses the Windows folder.
            listBox1->Items->Clear();
            String* dirs[] = Directory::GetDirectories(windir);
            int numDirs = dirs->get_Length();
            for (int i=0; i<numDirs; i++)
            {
                listBox1->Items->Add(dirs[i]);
            }
        }

        private: System::Void button6_Click(System::Object *  sender, System::EventArgs *  e)
        {
            // This code obtains a list of files. This example uses the Windows folder.
            listBox1->Items->Clear();
            String* files[]= Directory::GetFiles(this->windir);
            int numFiles = files->get_Length();
            for (int i=0; i<numFiles; i++)
            {
                listBox1->Items->Add(files[i]);
            }
        }
    };
}

//Form1.cpp
#include "stdafx.h"
#include "Form1.h"
#include <windows.h>

using namespace KB307398;

int APIENTRY _tWinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPTSTR    lpCmdLine,
                     int       nCmdShow)
{
    System::Threading::Thread::CurrentThread->ApartmentState = System::Threading::ApartmentState::STA;
    Application::Run(new Form1());
    return 0;
}

參考資料

如需詳細資訊，請造訪 Microsoft 支援服務。如需如何在適用於 C++ 的受控延伸模組中建立 Windows 窗體的詳細資訊，請參閱 ManagedCWinFormWiz Visual Studio .NET 說明中的範例。

共用方式為