Dapper + MediatR

Service1.cs

public class Service1 : IService1
{
    private readonly IDbConnection _connection;
    private readonly IDbTransaction _transaction;

    public Service1(IDbConnection connection, IDbTransaction transaction)
    {
        _connection = connection;
        _transaction = transaction;
    }

    public async Task CallDatabase()
    {
        await _connection.QueryAsync("", transaction: _transaction);
    }
}

Startup.cs

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddTransient<IService1, Service1>();
        services.AddTransient<IDbConnection>(provider => new SqlConnection(""));
        services.AddScoped(provider => provider.GetService<IDbConnection>().BeginTransaction());

        services.AddScoped(typeof(IPipelineBehavior<,>), typeof(TransactionBehavior<,>));
        
        services.AddControllers();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
    }
}

TransactionBehavior.cs

public class TransactionBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
{
    private readonly IDbTransaction _transaction;

    public TransactionBehavior(IDbTransaction transaction)
    {
        _transaction = transaction;
    }
    
    public async Task<TResponse> Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate<TResponse> next)
    {
        var response = default(TResponse);
        
        try
        {
            response = await next();
            _transaction.Commit();
        }
        catch (Exception e)
        {
            _transaction.Rollback();
        }
        
        return response;
    }
}