C#: تدريب: LINQ والملفات

using System;
using System.IO;
using System.Linq;
using System.Text.Json;
using System.Collections.Generic;

public class Student
{
    public string Name { get; set; }
    public int Score { get; set; }
}

class Program
{
    static void Main()
    {
        var students = new List<Student>
        {
            new Student { Name = "Zhang San", Score = 92 },
            new Student { Name = "Li Si", Score = 45 },
            new Student { Name = "Wang Wu", Score = 78 },
            new Student { Name = "Zhao Liu", Score = 88 },
            new Student { Name = "Qian Qi", Score = 55 },
            new Student { Name = "Sun Ba", Score = 95 },
            new Student { Name = "Zhou Jiu", Score = 33 },
            new Student { Name = "Wu Shi", Score = 71 }
        };

        string tempDir = Path.GetTempPath();
        string filePath = Path.Combine(tempDir, "students.json");

        var options = new JsonSerializerOptions { WriteIndented = true };
        string json = JsonSerializer.Serialize(students, options);
        File.WriteAllText(filePath, json);
        Console.WriteLine("Written to: " + filePath);

        string readJson = File.ReadAllText(filePath);
        var loaded = JsonSerializer.Deserialize<List<Student>>(readJson);

        double average = loaded.Average(s => s.Score);
        Console.WriteLine($"Average score: {average:F1}");

        var top3 = loaded.OrderByDescending(s => s.Score).Take(3);
        Console.WriteLine("Top three:");
        foreach (var s in top3)
        {
            Console.WriteLine($"  {s.Name} - {s.Score}");
        }

        int passCount = loaded.Count(s => s.Score >= 60);
        Console.WriteLine($"Pass count: {passCount}");

        var grouped = loaded.GroupBy(s => s.Score >= 90 ? "Excellent"
            : s.Score >= 60 ? "Pass" : "Fail");
        Console.WriteLine("Grade groups:");
        foreach (var group in grouped)
        {
            Console.WriteLine($"  {group.Key}: {string.Join(", ", group.Select(s => s.Name))}");
        }

        File.Delete(filePath);
    }
}

Written to: /tmp/students.json
Average score: 69.6
Top three:
  Sun Ba - 95
  Zhang San - 92
  Zhao Liu - 88
Pass count: 5
Grade groups:
  Excellent: Zhang San, Sun Ba
  Fail: Li Si, Qian Qi, Zhou Jiu
  Pass: Wang Wu, Zhao Liu, Wu Shi

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string tempDir = Path.GetTempPath();
        string logPath = Path.Combine(tempDir, "app.log");

        var lines = new List```<string>```
        {
            "[2025-01-10] [INFO] System started",
            "[2025-01-10] [WARN] Memory usage 80%",
            "[2025-01-11] [ERROR] Database connection failed",
            "[2025-01-11] [ERROR] Disk full",
            "[2025-01-12] [INFO] User login",
            "[2025-01-12] [ERROR] Database connection failed",
            "[2025-01-13] [WARN] CPU usage 90%",
            "[2025-01-13] [ERROR] Network timeout",
            "[2025-01-14] [INFO] Scheduled task completed",
            "[2025-01-14] [ERROR] Database connection failed"
        };
        File.WriteAllLines(logPath, lines);

        var logEntries = File.ReadAllLines(logPath)
            .Select(line =>
            {
                var parts = line.Split(']');
                return new
                {
                    Date = parts[0].TrimStart('[').Trim(),
                    Level = parts[1].TrimStart('[').Trim(),
                    Message = parts[2].Trim()
                };
            })
            .ToList();

        var levelCounts = logEntries
            .GroupBy(e => e.Level)
            .Select(g => new { Level = g.Key, Count = g.Count() })
            .OrderByDescending(x => x.Count);
        Console.WriteLine("Level counts:");
        foreach (var item in levelCounts)
        {
            Console.WriteLine($"  {item.Level}: {item.Count}");
        }

        var topError = logEntries
            .Where(e => e.Level == "ERROR")
            .GroupBy(e => e.Message)
            .OrderByDescending(g => g.Count())
            .First();
        Console.WriteLine($"Most frequent error: {topError.Key} ({topError.Count()} times)");

        var filtered = logEntries
            .Where(e => string.Compare(e.Date, "2025-01-11") >= 0
                     && string.Compare(e.Date, "2025-01-13") <= 0)
            .ToList();
        Console.WriteLine("Logs from Jan 11-13:");
        foreach (var entry in filtered)
        {
            Console.WriteLine($"  [{entry.Date}] [{entry.Level}] {entry.Message}");
        }

        File.Delete(logPath);
    }
}

Level counts:
  ERROR: 5
  INFO: 3
  WARN: 2
Most frequent error: Database connection failed (3 times)
Logs from Jan 11-13:
  [2025-01-11] [ERROR] Database connection failed
  [2025-01-11] [ERROR] Disk full
  [2025-01-12] [INFO] User login
  [2025-01-12] [ERROR] Database connection failed
  [2025-01-13] [WARN] CPU usage 90%
  [2025-01-13] [ERROR] Network timeout

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string workDir = Path.Combine(Path.GetTempPath(), "rename_demo");
        Directory.CreateDirectory(workDir);

        var demoFiles = new[] { "photo1.jpg", "photo2.jpg", "doc.txt", "notes.txt", "data.csv" };
        foreach (var f in demoFiles)
        {
            File.WriteAllText(Path.Combine(workDir, f), "demo");
        }
        Console.WriteLine("Original files:");
        foreach (var f in Directory.GetFiles(workDir))
        {
            Console.WriteLine("  " + Path.GetFileName(f));
        }

        string targetExt = ".txt";
        string prefix = "backup_";

        var filesToRename = Directory.GetFiles(workDir)
            .Where(f => Path.GetExtension(f).Equals(targetExt, StringComparison.OrdinalIgnoreCase))
            .ToList();

        Console.WriteLine($"\nFiltering extension {targetExt}:");
        foreach (var f in filesToRename)
        {
            string dir = Path.GetDirectoryName(f);
            string nameNoExt = Path.GetFileNameWithoutExtension(f);
            string newName = prefix + nameNoExt + targetExt;
            string newPath = Path.Combine(dir, newName);
            Console.WriteLine($"  {Path.GetFileName(f)} -> {newName}");
            File.Move(f, newPath);
        }

        Console.WriteLine("\nAfter renaming:");
        foreach (var f in Directory.GetFiles(workDir))
        {
            Console.WriteLine("  " + Path.GetFileName(f));
        }

        Directory.Delete(workDir, true);
    }
}

Original files:
  photo1.jpg
  photo2.jpg
  doc.txt
  notes.txt
  data.csv

Filtering extension .txt:
  doc.txt -> backup_doc.txt
  notes.txt -> backup_notes.txt

After renaming:
  photo1.jpg
  photo2.jpg
  backup_doc.txt
  backup_notes.txt
  data.csv