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Exercise 2: DI Service Lifetimes

Objective​

Understand Transient, Scoped, and Singleton service lifetimes through practical examples.

Implementation​

1. Create Services​

public interface IOperationService
{
    Guid OperationId { get; }
}

public class TransientService : IOperationService
{
    public Guid OperationId { get; } = Guid.NewGuid();
}

public class ScopedService : IOperationService
{
    public Guid OperationId { get; } = Guid.NewGuid();
}

public class SingletonService : IOperationService
{
    public Guid OperationId { get; } = Guid.NewGuid();
}

2. Register Services​

builder.Services.AddTransient<TransientService>();
builder.Services.AddScoped<ScopedService>();
builder.Services.AddSingleton<SingletonService>();

3. Create Test Endpoint​

app.MapGet("/lifetimes", (
    TransientService transient1,
    TransientService transient2,
    ScopedService scoped1,
    ScopedService scoped2,
    SingletonService singleton1,
    SingletonService singleton2) =>
{
    return new
    {
        Transient = new
        {
            Instance1 = transient1.OperationId,
            Instance2 = transient2.OperationId,
            AreSame = transient1.OperationId == transient2.OperationId
        },
        Scoped = new
        {
            Instance1 = scoped1.OperationId,
            Instance2 = scoped2.OperationId,
            AreSame = scoped1.OperationId == scoped2.OperationId
        },
        Singleton = new
        {
            Instance1 = singleton1.OperationId,
            Instance2 = singleton2.OperationId,
            AreSame = singleton1.OperationId == singleton2.OperationId
        }
    };
});

4. Test Multiple Requests​

# Request 1
curl http://localhost:5000/lifetimes

# Request 2 (compare IDs)
curl http://localhost:5000/lifetimes

Expected Results​

  • Transient: Different IDs every time (false, false)
  • Scoped: Same IDs within request, different across requests (true, false)
  • Singleton: Always same IDs (true, true)

Challenge​

Create a captive dependency scenario and demonstrate the problem.