.NET  

Leveraging Databases with .NET 9 in Financial Applications

In the fast-paced world of financial technology, high performance, scalability, and security are critical. .NET 9 brings significant improvements that make it an ideal platform for building modern, robust financial applications. When paired with a reliable database system, such as SQL Server, PostgreSQL, or MongoDB, .NET 9 becomes a powerhouse for building scalable financial software like banking platforms, portfolio trackers, or trading systems.

Why .NET 9 for Financial Applications?

.NET 9 is the latest Standard Term Support (STS) release and introduces performance enhancements, better minimal APIs, and more robust cloud-native support. These improvements are especially beneficial for data-intensive financial solutions.

Key features for financial apps include.

  • Minimal APIs for clean and fast web services.
  • Entity Framework Core 9 improvements for data access.
  • Improved JSON handling for APIs.
  • Async streaming and parallelism enhancements.

Database Choices in Financial Solutions

Here are common databases used in finance.

  • SQL Server: Ideal for transactional systems.
  • PostgreSQL: Open-source, supports complex queries.
  • MongoDB: Schema-less for dynamic financial data models.

Let’s dive into an example.

🏦 Example: Building a Portfolio Tracker API with .NET 9 and SQL Server

We’ll build a simple API that tracks user stock portfolios using Entity Framework Core and SQL Server.

1. Define the Data Model

public class Portfolio
{
    public int Id { get; set; }
    public string Owner { get; set; } = string.Empty;
    public List<Stock> Stocks { get; set; } = new();
}

public class Stock
{
    public int Id { get; set; }
    public string Symbol { get; set; } = string.Empty;
    public int Quantity { get; set; }
    public decimal PurchasePrice { get; set; }
    public int PortfolioId { get; set; }
}

2. Create the DbContext

public class FinanceDbContext : DbContext
{
    public FinanceDbContext(DbContextOptions<FinanceDbContext> options)
        : base(options) { }

    public DbSet<Portfolio> Portfolios => Set<Portfolio>();
    public DbSet<Stock> Stocks => Set<Stock>();
}

3. Configure Services and Connection String

builder.Services.AddDbContext<FinanceDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("FinanceDb")));

{
  "ConnectionStrings": {
    "FinanceDb": "Server=localhost;Database=FinanceDB;Trusted_Connection=True;"
  }
}

4. Create Minimal API Endpoints

app.MapGet("/portfolio/{id}", async (int id, FinanceDbContext db) =>
{
    var portfolio = await db.Portfolios
                             .Include(p => p.Stocks)
                             .FirstOrDefaultAsync(p => p.Id == id);

    return portfolio is Portfolio p 
        ? Results.Ok(p) 
        : Results.NotFound();
});
app.MapPost("/portfolio", async (Portfolio portfolio, FinanceDbContext db) =>
{
    db.Portfolios.Add(portfolio);
    await db.SaveChangesAsync();
    return Results.Created($"/portfolio/{portfolio.Id}", portfolio);
});

Real-World Use Case: Calculating Portfolio Value

In a real finance app, you'd want to calculate real-time portfolio value.

app.MapGet("/portfolio/{id}/value", async (int id, FinanceDbContext db) =>
{
    var portfolio = await db.Portfolios
        .Include(p => p.Stocks)
        .FirstOrDefaultAsync(p => p.Id == id);

    if (portfolio == null) 
        return Results.NotFound();

    decimal total = portfolio.Stocks
        .Sum(s => s.Quantity * s.PurchasePrice);

    return Results.Ok(new { portfolio.Id, portfolio.Owner, TotalValue = total });
});

Final Thoughts

.NET 9, paired with a relational database like SQL Server or PostgreSQL, enables developers to rapidly build secure and performant financial applications. Whether you're developing internal risk management tools, investment dashboards, or fintech APIs, .NET 9 offers a flexible and scalable solution.

🧰 Technologies Used.

  • .NET 9
  • Entity Framework Core
  • SQL Server
  • Minimal APIs

📈 Ideal Use Cases (Future potential articles I will write).

  • Investment Portfolio Trackers.
  • Personal Finance Dashboards.
  • Real-Time Trading Platforms.

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