Factory Design Pattern example in C# for exporting Person data to JSON or text formats with flexible factory implementation.

Factory.cs

using System.Text.Json;

// Client Code
public static class Program {
    public static void Main() {
        // Sample Data
        var people = new List<Person> {
            new("John", "Doe"),
            new("Jane", "Smith"),
            new("Alice", "Johnson")
        };

        Console.Write("Enter export format (json, text): ");
        var format = Console.ReadLine();

        try {
            // Use the factory to create the appropriate exporter
            var exporter = DataExporterFactory.CreateExporter(format);

            // Export the data
            var result = exporter.Export(people);
            Console.WriteLine(result);
        } catch (Exception ex) {
            Console.WriteLine($"Error: {ex.Message}");
        }
    }
}

// Define the Exporter Interface
public interface IDataExporter {
    string Export(List<Person> people);
}

// Define the Exporter Factory Interface
public interface IDataExporterFactory {
    IDataExporter CreateExporter();
}

// Implement Concrete Exporters

// JSON Exporter
public class JsonDataExporter : IDataExporter {
    public string Export(List<Person> people) =>
        JsonSerializer.Serialize(people, new JsonSerializerOptions { WriteIndented = true });
}

// JSON Exporter Factory
public class JsonDataExporterFactory : IDataExporterFactory {
    public IDataExporter CreateExporter() {
        // Simulate complex creation logic for JsonDataExporter
        return new JsonDataExporter();
    }
}

// Text Exporter
public class TextDataExporter : IDataExporter {
    public string Export(List<Person> people) =>
        string.Join(Environment.NewLine, people);
}

// Text Exporter Factory
public class TextDataExporterFactory : IDataExporterFactory {
    public IDataExporter CreateExporter() {
        // Simulate complex creation logic for TextDataExporter
        return new TextDataExporter();
    }
}

// Create the Abstract Factory
public static class DataExporterFactory {
    public static IDataExporter CreateExporter(string? format) {
        if (string.IsNullOrWhiteSpace(format)) throw new ArgumentNullException(nameof(format));

        IDataExporterFactory factory = format.ToLower() switch {
            "json" => new JsonDataExporterFactory(),
            "text" => new TextDataExporterFactory(),
            _ => throw new ArgumentException("Unsupported export format.")
        };

        // Use the factory to create the exporter
        return factory.CreateExporter();
    }
}

// Define the Person Record
public record Person(string Name, string Family) {
    public override string ToString() {
        return $"{Name} {Family}";
    }
}