我正在尝试使用 Autofac 添加 NLog 我的 Web Api 项目。但我有问题。
从 NuGet 安装 NLog 包后，我将以下文件添加到我的项目中。（由于关注不同的帖子和示例，可能会造成混淆）
ILogger.cs
public interface ILogger {
void Debug(string message);
void Trace(string message);
void Info(string message);
void Warning(string message);
void Error(string message);
void Error(string message, Exception exception);
void Fatal(string message);
void Fatal(string message, Exception exception);
}
记录器属性.cs
[AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Class)]
public class LoggerAttribute : Attribute {
public readonly string Name;
public LoggerAttribute(string name) {
Name = name;
}
}
NLogger.cs
public class NLogger : ILogger {
private readonly NLog.Logger logger;
public NLogger(Type loggerType) {
logger = LogManager.GetLogger(loggerType.FullName);
}
public void Debug(string message) {
logger.Debug(message);
}
public void Trace(string message) {
logger.Trace(message);
}
public void Info(string message) {
logger.Info(message);
}
public void Warning(string message) {
logger.Warn(message);
}
public void Error(string message) {
logger.Error(message);
}
public void Error(string message, Exception exception) {
logger.ErrorException(message, exception);
}
public void Fatal(string message) {
logger.Fatal(message);
}
public void Fatal(string message, Exception exception) {
logger.FatalException(message, exception);
}
}
NLogModule.cs
public class NLogModule : Module {
protected override void AttachToComponentRegistration(IComponentRegistry registry, IComponentRegistration registration) {
registration.Preparing += OnComponentPreparing;
}
static void OnComponentPreparing(object sender, PreparingEventArgs e) {
var typePreparing = e.Component.Activator.LimitType;
// By default, the name supplied to the logging instance is the name of the type in which it is being injected into.
string loggerName = typePreparing.FullName;
//If there is a class-level logger attribute, then promote its supplied name value instead as the logger name to use.
var loggerAttribute = (LoggerAttribute)typePreparing.GetCustomAttributes(typeof(LoggerAttribute), true).FirstOrDefault();
if(loggerAttribute != null) {
loggerName = loggerAttribute.Name;
}
e.Parameters = e.Parameters.Union(new Parameter[]
{
new ResolvedParameter(
(p, i) => p.ParameterType == typeof (ILogger),
(p, i) =>
{
// If the parameter being injected has its own logger attribute, then promote its name value instead as the logger name to use.
loggerAttribute = (LoggerAttribute)
p.GetCustomAttributes(typeof(LoggerAttribute),true).FirstOrDefault();
if (loggerAttribute != null)
{
loggerName = loggerAttribute.Name;
}
// Return a new Logger instance for injection, parameterised with the most appropriate name which we have determined above.
return LogManager.GetLogger(loggerName);
}),
// Always make an unamed instance of Logger available for use in delegate-based registration e.g.: Register((c,p) => new Foo(p.TypedAs<Logger>())
new TypedParameter(typeof(ILogger), LogManager.GetLogger(loggerName))
});
}
}
测试控制器.cs
public class TestController : ApiController
{
private IUnitOfWork uow;
private ILogger _logger;
// GET api/test
public TestController(IUnitOfWork unitOfWork, ILogger logger) {
uow = unitOfWork;
_logger = logger;
}
...
}
引导程序.cs
var builder = new ContainerBuilder();
// Register the Web API controllers.
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
// Register other dependencies.
builder.RegisterType<UnitOfWork>().As<IUnitOfWork>().InstancePerApiRequest();
builder.RegisterType<NLogger>().As<ILogger>().InstancePerApiRequest();
builder.RegisterModule(new NLogModule());
builder.Register((c, p) => new TestController(p.TypedAs<UnitOfWork>(), p.TypedAs<NLogger>()));
// Build the container.
var container = builder.Build();
// Create the depenedency resolver.
var resolver = new AutofacWebApiDependencyResolver(container);
// Configure Web API with the dependency resolver.
GlobalConfiguration.Configuration.DependencyResolver = resolver;
我无法让它工作，每一个变化都会导致不同的错误。
当前代码导致以下错误。
<Error>
<Message>An error has occurred.</Message>
<ExceptionMessage>Sequence contains no elements</ExceptionMessage>
<ExceptionType>System.InvalidOperationException</ExceptionType>
<StackTrace>
at System.Linq.Enumerable.First[TSource](IEnumerable`1 source) at Autofac.ParameterExtensions.ConstantValue[TParameter,TValue](IEnumerable`1 parameters, Func`2 predicate) at Autofac.ParameterExtensions.TypedAs[T](IEnumerable`1 parameters) at TestAPI.Bootstrapper.<SetAutofacWebAPIServices>b__0(IComponentContext c, IEnumerable`1 p) in d:\Projects\RadoreAPIs\TestAPI\Bootstrapper.cs:line 32 at Autofac.Builder.RegistrationBuilder.<>c__DisplayClass1`1.<ForDelegate>b__0(IComponentContext c, IEnumerable`1 p) at Autofac.Core.Activators.Delegate.DelegateActivator.ActivateInstance(IComponentContext context, IEnumerable`1 parameters) at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable`1 parameters) at Autofac.Core.Resolving.InstanceLookup.Execute() at Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, IComponentRegistration registration, IEnumerable`1 parameters) at Autofac.Core.Resolving.ResolveOperation.Execute(IComponentRegistration registration, IEnumerable`1 parameters)
</StackTrace>
</Error>