Add Error Logging

.NET has built-in structured logging via the ILogger interface

Add Global Error Handling

If you want centralized error handling, you can use middleware

This will log any unhandled exception, and return a generic 500 error to the client

In Program.cs, add before app.Run()

app.UseExceptionHandler(errorApp =>
{
    errorApp.Run(async context =>
    {
        var logger = context.RequestServices.GetRequiredService<ILogger<Program>>();
        var exception = context.Features.Get<Microsoft.AspNetCore.Diagnostics.IExceptionHandlerFeature>()?.Error;

        logger.LogError(exception, "Unhandled exception occurred");

        context.Response.StatusCode = 500;
        await context.Response.WriteAsJsonAsync(new { error = "An unexpected error occurred." });
    });
});

Save Logs to a File

Serilog is a powerful structured logging library that allows us to create structured logs and save them to a file

First, we need to install some required Nuget packages

Serilog.AspNetCore
Serilog.Sinks.Console
Serilog.Sinks.File

Update Program.cs to use Serilog. Add the following to the beginning of the file

Log.Logger = new LoggerConfiguration()
    .WriteTo.Console()
    .WriteTo.File("Logs/log.txt", rollingInterval: RollingInterval.Day)
    .Enrich.FromLogContext()
    .CreateLogger();

Add the following to the builder

builder.Host.UseSerilog();

Then finally, add this to the very end of the file

Log.CloseAndFlush();

This line ensures that if the application crashes, the error will still be logged to the log file

The completed Program.cs file should look like this

using CrudAppAPI.Data;
using CrudAppAPI.Endpoints;
using CrudAppAPI.Services;
using Serilog;

Log.Logger = new LoggerConfiguration()
    .WriteTo.Console()
    .WriteTo.File("Logs/log.txt", rollingInterval: RollingInterval.Day)
    .Enrich.FromLogContext()
    .CreateLogger();

var builder = WebApplication.CreateBuilder(args);

builder.Host.UseSerilog();
builder.Services.AddOpenApi();
builder.Services.AddScoped<TaskService>();
builder.Services.AddScoped<IDbConnectionFactory, SqlConnectionFactory>();

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.MapOpenApi();
}

app.UseHttpsRedirection();

app.MapTaskEndpoints();

app.UseExceptionHandler(errorApp =>
{
    errorApp.Run(async context =>
    {
        var logger = context.RequestServices.GetRequiredService<ILogger<Program>>();
        var exception = context.Features.Get<Microsoft.AspNetCore.Diagnostics.IExceptionHandlerFeature>()?.Error;

        logger.LogError(exception, "Unhandled exception occurred");

        context.Response.StatusCode = 500;
        await context.Response.WriteAsJsonAsync(new { error = "An unexpected error occurred." });
    });
});

app.Run();
Log.CloseAndFlush();

Add validation results to Logs

app.MapPost("/api/tasks", async (
    CreateTaskDto dto,
    TaskService service,
    IValidator<CreateTaskDto> validator,
    ILogger<Program> logger) =>
{
    var validationResult = await validator.ValidateAsync(dto);

    if (!validationResult.IsValid)
    {
        logger.LogWarning("Validation failed for CreateTaskDto: {@Errors}", validationResult.Errors);
        return Results.BadRequest(validationResult.Errors);
    }

    await service.AddTaskAsync(dto);
    return Results.Ok();
});

10 July 2025