Visual C# 程式設計實用技巧彙總：檔案版本、屬性、字串格式化、IO、對話框

編輯：關於C語言

前言

本文彙總 C# 開發中高頻使用的實用技巧，涵蓋檔案版本資訊、檔案屬性操作、字串格式化、檔案 IO、對話框使用等，代碼可直接複製應用。

1. 取得檔案版本資訊


using System.Diagnostics;

public static string GetFileVersion(string filePath)
{
    if (!File.Exists(filePath)) return null;
    
    FileVersionInfo info = FileVersionInfo.GetVersionInfo(filePath);
    return $"版本: {info.FileVersion}\n" +
           $"產品: {info.ProductName}\n" +
           $"公司: {info.CompanyName}\n" +
           $"著作權: {info.LegalCopyright}\n" +
           $"描述: {info.FileDescription}";
}

// 使用
string version = GetFileVersion(@"D:\MyApp\MyLib.dll");

2. 檔案屬性操作：移除唯讀並覆寫複製


public static void ForceCopy(string source, string destination)
{
    if (File.Exists(destination))
    {
        FileInfo fi = new FileInfo(destination);
        // 移除唯讀屬性
        if ((fi.Attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly)
        {
            fi.Attributes = FileAttributes.Normal;
        }
        File.Delete(destination);
    }
    
    File.Copy(source, destination, true); // true = 允許覆寫
}

3. 字串格式化與轉換

字串轉數值 (安全轉換)


string str = "12345";
int number = int.TryParse(str, out int result) ? result : 0;
// 或
int number2 = Convert.ToInt32(str); // 例外較多，建議 TryParse

字串補齊 (PadLeft/PadRight)


string code = "42";
// 左補零至 6 位: "000042"
string padded = code.PadLeft(6, '0');

// 右補空格至 30 字元
string line = "項目名稱".PadRight(30, ' ');

格式化輸出 (字串插值 / composite formatting)


int year = 2024, month = 1, day = 15;
decimal price = 1234.56m;

// 字串插值 (C# 6+)
string s1 = $"{year:D4}/{month:D2}/{day:D2}  價格: {price:C2}";

// 複合格式
string s2 = string.Format("{0:D4}/{1:D2}/{2:D2}  價格: {3:C2}", year, month, day, price);

// 自訂日期格式
string s3 = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff");

4. 檔案逐行讀寫

逐行讀取 (記憶體效率佳)


public static IEnumerable ReadLinesLazy(string path)
{
    if (!File.Exists(path)) yield break;
    
    using (var reader = new StreamReader(path, Encoding.UTF8))
    {
        string line;
        while ((line = reader.ReadLine()) != null)
            yield return line;
    }
}

// 使用
foreach (string line in ReadLinesLazy("log.txt"))
{
    Console.WriteLine(line);
}

逐行寫入


public static void WriteLines(string path, IEnumerable lines)
{
    using (var writer = new StreamWriter(path, false, Encoding.UTF8)) // false = 覆寫
    {
        foreach (string line in lines)
            writer.WriteLine(line);
    }
}

// 追加模式
public static void AppendLine(string path, string line)
{
    using (var writer = new StreamWriter(path, true, Encoding.UTF8)) // true = 追加
    {
        writer.WriteLine(line);
    }
}

5. 檔案/目錄存在性檢查


bool fileExists = File.Exists(@"C:\Data\config.json");
bool dirExists = Directory.Exists(@"C:\Data\Backups");

// 確保目錄存在
string dir = Path.GetDirectoryName(filePath);
if (!Directory.Exists(dir))
    Directory.CreateDirectory(dir); // 遞迴建立所有父目錄

6. OpenFileDialog 與 FolderBrowserDialog

開啟檔案對話框


using System.Windows.Forms;

public static string ShowOpenFileDialog(string initialDir = null, string filter = "所有檔案 (*.*)|*.*")
{
    using (var dialog = new OpenFileDialog())
    {
        dialog.InitialDirectory = initialDir ?? Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
        dialog.Filter = filter;
        dialog.FilterIndex = 1;
        dialog.RestoreDirectory = true;
        dialog.Multiselect = false;
        dialog.Title = "請選擇檔案";
        
        return dialog.ShowDialog() == DialogResult.OK ? dialog.FileName : null;
    }
}

// 多選
public static string[] ShowOpenFilesDialog()
{
    using (var dialog = new OpenFileDialog { Multiselect = true })
    {
        return dialog.ShowDialog() == DialogResult.OK ? dialog.FileNames : Array.Empty();
    }
}

選擇資料夾對話框


public static string ShowFolderDialog(string description = "請選擇資料夾")
{
    using (var dialog = new FolderBrowserDialog())
    {
        dialog.Description = description;
        dialog.RootFolder = Environment.SpecialFolder.MyComputer;
        dialog.ShowNewFolderButton = true;
        
        return dialog.ShowDialog() == DialogResult.OK ? dialog.SelectedPath : null;
    }
}

7. 進階技巧：大檔案複製進度回報


public static async Task CopyWithProgressAsync(string source, string dest, IProgress progress, CancellationToken ct = default)
{
    const int bufferSize = 81920; // 80KB
    long totalBytes = new FileInfo(source).Length;
    long copiedBytes = 0;
    
    using (var srcStream = new FileStream(source, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize, true))
    using (var dstStream = new FileStream(dest, FileMode.Create, FileAccess.Write, FileShare.None, bufferSize, true))
    {
        byte[] buffer = new byte[bufferSize];
        int bytesRead;
        
        while ((bytesRead = await srcStream.ReadAsync(buffer, ct)) > 0)
        {
            await dstStream.WriteAsync(buffer.AsMemory(0, bytesRead), ct);
            copiedBytes += bytesRead;
            progress?.Report((double)copiedBytes / totalBytes * 100);
        }
    }
}

// 使用
var progress = new Progress(p => Console.WriteLine($"進度: {p:F1}%"));
await CopyWithProgressAsync("big.iso", "copy.iso", progress);

8. 路徑操作最佳實踐


string path = @"C:\Projects\MyApp\bin\Debug\app.exe";

Path.GetFileName(path);        // "app.exe"
Path.GetFileNameWithoutExtension(path); // "app"
Path.GetExtension(path);       // ".exe"
Path.GetDirectoryName(path);   // "C:\Projects\MyApp\bin\Debug"
Path.GetFullPath("..\\config.json");    // 解析相對路徑
Path.Combine("C:\\Data", "logs", "app.log"); // 安全組合路徑
Path.ChangeExtension(path, ".bak"); // "app.bak"
Path.GetRandomFileName();      // 產生隨機檔名 (如 "abc123.tmp")
Path.GetTempFileName();        // 建立暫存檔並回傳路徑