NDLRLOG005: No accessible ILogger

Cause

A method marked with [NeedlrLoggerMessage] has no logger to use.

Rule Description

The generated body needs an ILogger (or ILogger<T>) to write to:

• An instance method must have an ILogger field or property on its containing type (or a base type).
• A static method must take an ILogger parameter.

When neither is present, the generator cannot emit a working body.

How to Fix

public partial class OrderService
{
    // WRONG: no ILogger field, so an instance logging method has nothing to write to
    [NeedlrLoggerMessage(Level = LogLevel.Warning, Message = "Failed {OrderId}")]
    public partial void LogFailedWrong(int orderId, Exception error);
}

public partial class OrderServiceFixed
{
    private readonly ILogger _logger;          // CORRECT: instance method uses this field

    public OrderServiceFixed(ILogger<OrderServiceFixed> logger) => _logger = logger;

    [NeedlrLoggerMessage(Level = LogLevel.Warning, Message = "Failed {OrderId}")]
    public partial void LogFailed(int orderId, Exception error);
}

public static partial class Log
{
    // CORRECT: static method takes an ILogger parameter
    [NeedlrLoggerMessage(Level = LogLevel.Warning, Message = "Failed {OrderId}")]
    public static partial void Failed(ILogger logger, int orderId, Exception error);
}

See Also

• Cancellation-Aware Logging