Sample Data Generator for Task #1 (.NET 6)

Program.cs

// See https://aka.ms/new-console-template for more information
int count = 6;

var products = Enumerable.Range(1001, 20).ToArray();

for (int i = 1; i <= count; i++)
{
    int recordsCount = (int)Math.Pow(10, i);
    var fileName = $"Data/Data{recordsCount}.csv";
    Directory.CreateDirectory("Data");
    using (FileStream fs = new FileStream(fileName, FileMode.Create))
    {
        WriteRecords(fs, recordsCount);
    }

    Console.WriteLine($"File {fileName} is written to disk");
}

void WriteRecords(FileStream fs, int recordsCount)
{
    using (StreamWriter sw = new StreamWriter(fs))
    {
        sw.WriteLine("RecordNumber | ProductId | Price | Quantity");
        for (int i = 0; i < recordsCount; i++)
        {
            sw.WriteLine("{0} | {1} | {2} | {3}", 
                i + 1, 
                products[Random.Shared.Next(products.Length)],
                Random.Shared.Next(100, 100000), 
                Random.Shared.Next(1, 1000));
        }
    }
}