Logging Configuration with log4net in Gestión Clínica API

The Gestión Clínica API employs two complementary logging mechanisms that serve distinct purposes. The first is log4net, which captures unexpected exceptions and infrastructure errors to a rolling text file on the server filesystem. The second is a database audit log powered by LogBL, which records every intentional user action — patient registration, insurance plan update, login — as a structured row in the database, giving clinic administrators a permanent, queryable trail of who did what and when.

Mechanism 1 — log4net Exception Logging

Configuration in Web.config

log4net is configured entirely within Web.config using a dedicated <log4net> section. The section handler is declared in <configSections> at the top of the file:

<configSections>
  <section
    name="log4net"
    type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>

The log4net section itself defines two appenders and a root logger:

<log4net>

  <!-- Writes to the Visual Studio Output / Debug console -->
  <appender name="DebugAppender" type="log4net.Appender.DebugAppender">
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %-5level %logger - %message%newline" />
    </layout>
  </appender>

  <!-- Writes to Log/Log.txt with size-based rolling -->
  <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
    <file value="Log/Log.txt" />
    <appendToFile value="true" />
    <rollingStyle value="Size" />
    <maxSizeRollBackups value="10" />
    <maximumFileSize value="1MB" />
    <staticLogFileName value="true" />
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %-5level %logger - %message%newline" />
    </layout>
  </appender>

  <!-- Root logger: capture everything (ALL level), send to both appenders -->
  <root>
    <level value="All" />
    <appender-ref ref="DebugAppender" />
    <appender-ref ref="RollingFileAppender" />
  </root>

</log4net>

Rolling File Appender Settings

Setting	Value	Meaning
`file`	`Log/Log.txt`	Path relative to the IIS application root
`appendToFile`	`true`	New entries are appended, not overwriting the file
`rollingStyle`	`Size`	Roll files when size limit is reached
`maxSizeRollBackups`	`10`	Keep up to 10 backup files (`Log.txt.1` … `Log.txt.10`)
`maximumFileSize`	`1MB`	Roll to a new backup when current file exceeds 1 MB
`staticLogFileName`	`true`	Active log always named `Log.txt`; backups get numeric suffixes

Pattern Layout

Each log entry uses the pattern %date %-5level %logger - %message%newline, which produces lines such as:

2024-03-15 09:42:17,334 ERROR  - Mensaje: Object reference not set Trace: at Romsoft…

Token	Output
`%date`	Full timestamp including milliseconds
`%-5level`	Log level left-padded to 5 characters (`ERROR`, `WARN` , `INFO` )
`%logger`	Logger name (empty string for the root logger)
`%message`	The formatted message
`%newline`	Platform-appropriate line terminator

Bootstrapping log4net

log4net is initialized once in Global.asax.cs during Application_Start:

protected void Application_Start()
{
    GlobalConfiguration.Configure(WebApiConfig.Register);
    log4net.Config.XmlConfigurator.Configure(); // reads <log4net> from Web.config
    AutoMapperConfiguration.Configure();
}

Using the Logger in Controllers

BaseController exposes a shared root logger as a protected static field:

public class BaseController : ApiController
{
    protected static readonly ILog Logger =
        LogManager.GetLogger(string.Empty); // binds to root logger

    protected void LogError(Exception exception)
    {
        Logger.Error(string.Format(
            "Mensaje: {0} Trace: {1}",
            exception.Message,
            exception.StackTrace));
    }

    protected void LogError(string mensaje)
    {
        Logger.Error(mensaje);
    }
}

Every controller action wraps its body in a try/catch and calls LogError(ex) in the catch block. This ensures that no exception is silently swallowed — it always lands in Log/Log.txt alongside a JsonResponse with Success=false.

Mechanism 2 — Database Audit Log

The `Log` Entity

The Log class in Romsoft.GESTIONCLINICA.Entidades defines the schema of the audit record:

public class Log
{
    public int      Id              { get; set; }
    public string   DireccionIP     { get; set; }  // Client IP address
    public string   Usuario         { get; set; }  // Username performing the action
    public string   Mensaje         { get; set; }  // Outcome message
    public string   Controlador     { get; set; }  // Controller name (e.g. "Usuario")
    public string   Accion          { get; set; }  // Action name (e.g. "Add", "Update")
    public DateTime FechaRegistro   { get; set; }  // Timestamp (set by DB default)
    public string   Objeto          { get; set; }  // JSON-serialized request DTO
    public int?     Identificador   { get; set; }  // ID of the affected record (nullable)
}

Audit Log Fields

Field	Type	Description
`Id`	`int`	Auto-increment primary key
`DireccionIP`	`string`	IP address of the calling client
`Usuario`	`string`	Username from the DTO (e.g., `pacienteDTO.UsuarioCreacion`)
`Mensaje`	`string`	The `JsonResponse.Message` returned to the client
`Controlador`	`string`	Module identifier string from `Mensajes` (e.g., `"Usuario"`)
`Accion`	`string`	Operation name: `"Add"`, `"Update"`, `"Delete"`, `"Login"`
`FechaRegistro`	`DateTime`	Timestamp of the action, typically set by a SQL `DEFAULT GETDATE()`
`Objeto`	`string`	Full JSON serialization of the DTO that was sent (via `JsonConvert.SerializeObject`)
`Identificador`	`int?`	Primary key of the affected row (0 for inserts before the ID is known)

Writing an Audit Record

The LogBL singleton provides a single Add method:

public class LogBL : Singleton<LogBL>, ILogBL<Log>
{
    public int Add(Log entity)
    {
        return LogRepository.Instancia.Add(entity);
    }
}

Controllers call LogBL.Instancia.Add(new Log { … }) inside the try block, after the primary business operation completes, so that the audit record captures the real outcome — including any warning message:

[HttpPost]
public JsonResponse Add(ADM_PACIENTEDTO pacienteDTO)
{
    var jsonResponse = new JsonResponse { Success = true };
    try
    {
        var paciente = MapperHelper.Map<ADM_PACIENTEDTO, ADM_PACIENTE>(pacienteDTO);
        // … business logic …

        // Audit record written regardless of Success/Warning outcome
        LogBL.Instancia.Add(new Log
        {
            Accion       = Mensajes.Add,                          // "Add"
            Controlador  = Mensajes.UsuarioController,            // "Usuario"
            Identificador = 0,
            Mensaje      = jsonResponse.Message,
            Usuario      = pacienteDTO.UsuarioCreacion,
            Objeto       = JsonConvert.SerializeObject(pacienteDTO)
        });
    }
    catch (Exception ex)
    {
        LogError(ex);                          // log4net — stack trace to file
        jsonResponse.Success = false;
        jsonResponse.Message = Mensajes.IntenteloMasTarde;
    }
    return jsonResponse;
}

Every Add, Update, Delete, and Login operation writes an audit record to the database, even when the operation returns a business warning (e.g., duplicate record). This means the audit table captures all attempts, not just successful ones. Exception failures are recorded by log4net only (to Log/Log.txt), since the LogBL.Instancia.Add call is inside the try block and would not execute if the exception occurs before it.

Action Name Constants

The Mensajes class defines string constants used for the Accion field:

public static string Add             = "Add";
public static string Update          = "Update";
public static string Delete          = "Delete";
public static string Login           = "Login";
public static string AddDetalleGrupal = "AddDetalleGrupal";

Comparing the Two Mechanisms

Aspect	log4net (`Log/Log.txt`)	Database Audit Log
Triggered by	Unhandled exceptions in `catch` block	Every CRUD/Login action in `try` block
Storage	Rolling text file on IIS server	`Log` table in SQL Server
Queryable	No (text file)	Yes (SQL `SELECT`)
Contains stack trace	Yes	No
Contains request payload	No	Yes (JSON-serialized DTO)
Survives server restart	Yes (persistent file)	Yes (persistent database)
Purpose	Developer/ops incident investigation	Clinical compliance and audit trail

Set up a scheduled job or SQL Agent task to archive or purge rows from the Log audit table older than a compliance-defined retention period (e.g., 5 years for Peruvian clinical records). The FechaRegistro column is the natural partition key for this archival process.

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Architecture

Configuration

Logging Configuration with log4net in Gestión Clínica API

Mechanism 1 — log4net Exception Logging

Configuration in Web.config

Rolling File Appender Settings

Pattern Layout

Bootstrapping log4net

Using the Logger in Controllers

Mechanism 2 — Database Audit Log

The `Log` Entity

Audit Log Fields

Writing an Audit Record

Action Name Constants

Comparing the Two Mechanisms

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Architecture

Configuration

Documentation Index

​Mechanism 1 — log4net Exception Logging

​Configuration in Web.config

​Rolling File Appender Settings

​Pattern Layout

​Bootstrapping log4net

​Using the Logger in Controllers

​Mechanism 2 — Database Audit Log

​The Log Entity

​Audit Log Fields

​Writing an Audit Record

​Action Name Constants

​Comparing the Two Mechanisms

Build docs developers (and LLMs) love

Mechanism 1 — log4net Exception Logging

Configuration in Web.config

Rolling File Appender Settings

Pattern Layout

Bootstrapping log4net

Using the Logger in Controllers

Mechanism 2 — Database Audit Log

The `Log` Entity

Audit Log Fields

Writing an Audit Record

Action Name Constants

Comparing the Two Mechanisms