Logging

NCalc integrates with Microsoft.Extensions.Logging. There is no built-in console or trace switch anymore. Logging follows the standard .NET logging pipeline and is only emitted when you provide loggers through dependency injection.

Default behavior

If you use NCalc without DI, the built-in singleton implementations use NullLoggerFactory. In practice, this means logging is disabled by default.

This applies to:

• LogicalExpressionCache.GetInstance()
• LogicalExpressionFactory.GetInstance()

Logged events

The current built-in log messages are:

• Information EventId=0: expression retrieved from cache
• Information EventId=1: expression added to cache
• Information EventId=2: expression removed from cache
• Error EventId=3: error creating a logical expression

Using logging with DI

When you register NCalc with NCalc.DependencyInjection, NCalc uses the application's configured ILoggerFactory for services created by the container.

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using NCalc.DependencyInjection;

var services = new ServiceCollection();

services.AddLogging(builder =>
{
    builder.AddConsole();
    builder.SetMinimumLevel(LogLevel.Information);
});

services.AddNCalc();

With the default registrations, ILogicalExpressionCache is created by DI, so cache events are logged through ILogger<LogicalExpressionCache>.

Important note about ILogicalExpressionFactory

AddNCalc() currently registers ILogicalExpressionFactory by returning LogicalExpressionFactory.GetInstance(). That singleton is created with NullLoggerFactory, so the built-in parse-error log is not emitted through DI in that default registration.

If you want logging from the logical expression factory as well, replace the registration with your own implementation of ILogicalExpressionFactory, or register a DI-created factory instance yourself.

For general guidance on configuring providers, filters, and sinks, see the Microsoft logging documentation.