Using.NET 9 Databases 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

2. Create the DbContext

<span class="token keyword keyword-public">public</span> <span class="token keyword keyword-class">class</span> <span class="token class-name">FinanceDbContext</span> <span class="token punctuation">:</span> <span class="token type-list"><span class="token class-name">DbContext</span></span>
<span class="token punctuation">{</span>
    <span class="token keyword keyword-public">public</span> <span class="token function">FinanceDbContext</span><span class="token punctuation">(</span><span class="token class-name">DbContextOptions<span class="token punctuation">&lt;</span>FinanceDbContext<span class="token punctuation">&gt;</span></span> options<span class="token punctuation">)</span>
        <span class="token punctuation">:</span> <span class="token keyword keyword-base">base</span><span class="token punctuation">(</span>options<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token punctuation">}</span>

    <span class="token keyword keyword-public">public</span> <span class="token return-type class-name">DbSet<span class="token punctuation">&lt;</span>Portfolio<span class="token punctuation">&gt;</span></span> Portfolios <span class="token operator">=&gt;</span> <span class="token generic-method"><span class="token function">Set</span><span class="token generic class-name"><span class="token punctuation">&lt;</span>Portfolio<span class="token punctuation">&gt;</span></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword keyword-public">public</span> <span class="token return-type class-name">DbSet<span class="token punctuation">&lt;</span>Stock<span class="token punctuation">&gt;</span></span> Stocks <span class="token operator">=&gt;</span> <span class="token generic-method"><span class="token function">Set</span><span class="token generic class-name"><span class="token punctuation">&lt;</span>Stock<span class="token punctuation">&gt;</span></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

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

4. Create Minimal API Endpoints

Real-World Use Case: Calculating Portfolio Value

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

app<span class="token punctuation">.</span><span class="token function">MapGet</span><span class="token punctuation">(</span><span class="token string">"/portfolio/{id}/value"</span><span class="token punctuation">,</span> <span class="token keyword keyword-async">async</span> <span class="token punctuation">(</span><span class="token class-name"><span class="token keyword keyword-int">int</span></span> id<span class="token punctuation">,</span> <span class="token class-name">FinanceDbContext</span> db<span class="token punctuation">)</span> <span class="token operator">=&gt;</span>
<span class="token punctuation">{</span>
    <span class="token class-name"><span class="token keyword keyword-var">var</span></span> portfolio <span class="token operator">=</span> <span class="token keyword keyword-await">await</span> db<span class="token punctuation">.</span>Portfolios
        <span class="token punctuation">.</span><span class="token function">Include</span><span class="token punctuation">(</span>p <span class="token operator">=&gt;</span> p<span class="token punctuation">.</span>Stocks<span class="token punctuation">)</span>
        <span class="token punctuation">.</span><span class="token function">FirstOrDefaultAsync</span><span class="token punctuation">(</span>p <span class="token operator">=&gt;</span> p<span class="token punctuation">.</span>Id <span class="token operator">==</span> id<span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token keyword keyword-if">if</span> <span class="token punctuation">(</span>portfolio <span class="token operator">==</span> <span class="token keyword keyword-null">null</span><span class="token punctuation">)</span>
        <span class="token keyword keyword-return">return</span> Results<span class="token punctuation">.</span><span class="token function">NotFound</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token class-name"><span class="token keyword keyword-decimal">decimal</span></span> total <span class="token operator">=</span> portfolio<span class="token punctuation">.</span>Stocks
        <span class="token punctuation">.</span><span class="token function">Sum</span><span class="token punctuation">(</span>s <span class="token operator">=&gt;</span> s<span class="token punctuation">.</span>Quantity <span class="token operator">*</span> s<span class="token punctuation">.</span>PurchasePrice<span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token keyword keyword-return">return</span> Results<span class="token punctuation">.</span><span class="token function">Ok</span><span class="token punctuation">(</span><span class="token keyword keyword-new">new</span> <span class="token punctuation">{</span> portfolio<span class="token punctuation">.</span>Id<span class="token punctuation">,</span> portfolio<span class="token punctuation">.</span>Owner<span class="token punctuation">,</span> TotalValue <span class="token operator">=</span> total <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

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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