我查看了这个链接http://www.asp.net/web-api/overview/web-api-routing-and-actions/web-api-global-error-handling。在这个链接中他们提到了这样的
class OopsExceptionHandler : ExceptionHandler
{
public override void HandleCore(ExceptionHandlerContext context)
{
context.Result = new TextPlainErrorResult
{
Request = context.ExceptionContext.Request,
Content = "Oops! Sorry! Something went wrong." +
"Please contact [email protected] so we can try to fix it."
};
}
private class TextPlainErrorResult : IHttpActionResult
{
public HttpRequestMessage Request { get; set; }
public string Content { get; set; }
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
HttpResponseMessage response =
new HttpResponseMessage(HttpStatusCode.InternalServerError);
response.Content = new StringContent(Content);
response.RequestMessage = Request;
return Task.FromResult(response);
}
}
}
我不知道如何在我的Web API操作中调用此类。所以任何人都可以使用这个ExceptionHandler给我完整的样本。
在您的WebApi配置中，您需要添加以下行：
config.Services.Replace(typeof (IExceptionHandler), new OopsExceptionHandler());
还要确保已创建实现IExceptionHandler的基本ExceptionHandler类：
public class ExceptionHandler : IExceptionHandler
{
public virtual Task HandleAsync(ExceptionHandlerContext context,
CancellationToken cancellationToken)
{
if (!ShouldHandle(context))
{
return Task.FromResult(0);
}
return HandleAsyncCore(context, cancellationToken);
}
public virtual Task HandleAsyncCore(ExceptionHandlerContext context,
CancellationToken cancellationToken)
{
HandleCore(context);
return Task.FromResult(0);
}
public virtual void HandleCore(ExceptionHandlerContext context)
{
}
public virtual bool ShouldHandle(ExceptionHandlerContext context)
{
return context.CatchBlock.IsTopLevel;
}
}
请注意，这只会处理其他地方未处理的异常（例如，通过异常过滤器）。
相反，您可以简单地从ExceptionHandler继承并覆盖Handle方法。
public class MyExceptionHandler: ExceptionHandler
{
public override void Handle(ExceptionHandlerContext context)
{
//TODO: Do what you need to do
base.Handle(context);
}
}
ExceptionHandler实现IExceptionHandler并管理基本核心机制（如异步和异常应该处理或不处理）。
像这样使用你的异常处理程序：
config.Services.Replace(typeof(IExceptionHandler), new MyExceptionHandler());
This page解释了如何实现IExceptionHandler，但是有一些拼写错误并且代码没有反映最新版本的WebApi。
没有关于System.Web.Http.ExceptionHandling命名空间的文档（有点像NuDoq）。
所以..
使用.NET assembly decompiler
看看the source code on GitHub，我看到ExceptionHandler类实现了IExceptionHandler并且有一些虚拟方法。
ExceptionHandler看起来像这样：
namespace System.Web.Http.ExceptionHandling
{
/// <summary>Represents an unhandled exception handler.</summary>
public abstract class ExceptionHandler: IExceptionHandler
{
/// <returns>Returns <see cref="T:System.Threading.Tasks.Task" />.</returns>
Task IExceptionHandler.HandleAsync(ExceptionHandlerContext context, CancellationToken cancellationToken)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
ExceptionContext arg_14_0 = context.ExceptionContext;
if (!this.ShouldHandle(context))
{
return TaskHelpers.Completed();
}
return this.HandleAsync(context, cancellationToken);
}
/// <summary>When overridden in a derived class, handles the exception asynchronously.</summary>
/// <returns>A task representing the asynchronous exception handling operation.</returns>
/// <param name="context">The exception handler context.</param>
/// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
public virtual Task HandleAsync(ExceptionHandlerContext context, CancellationToken cancellationToken)
{
this.Handle(context);
return TaskHelpers.Completed();
}
/// <summary>When overridden in a derived class, handles the exception synchronously.</summary>
/// <param name="context">The exception handler context.</param>
public virtual void Handle(ExceptionHandlerContext context)
{
}
/// <summary>Determines whether the exception should be handled.</summary>
/// <returns>true if the exception should be handled; otherwise, false.</returns>
/// <param name="context">The exception handler context.</param>
public virtual bool ShouldHandle(ExceptionHandlerContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
ExceptionContext exceptionContext = context.ExceptionContext;
ExceptionContextCatchBlock catchBlock = exceptionContext.CatchBlock;
return catchBlock.IsTopLevel;
}
}
}
您可以清楚地看到ShouldHandle是使用ExceptionContextCatchBlock.IsTopLevel实现的，HandleAsync调用Handle :)
我希望这会有所帮助，直到完整的文档显示出来。
根据Jon Susiak的回答，您需要使用：
config.Services.Replace(typeof (IExceptionHandler), new OopsExceptionHandler());
请注意Replace电话，而不是Add。原因是根据此链接中的文章：
Global Error Handling in ASP.NET Web API 2
方案概述
我们提供了两个新的用户可替换服务IExceptionLogger和IExceptionHandler来记录和处理未处理的异常。
服务非常相似，有两个主要区别：
我们支持注册多个异常记录器，但只支持一个异常处理程序。
由于默认情况下已经注册了处理程序，因此无法添加其他处理程序。
public DefaultServices(HttpConfiguration configuration)
{
if (configuration == null)
throw System.Web.Http.Error.ArgumentNull("configuration");
this._configuration = configuration;
this.SetSingle<IActionValueBinder>((IActionValueBinder) new DefaultActionValueBinder());
this.SetSingle<IApiExplorer>((IApiExplorer) new ApiExplorer(configuration));
this.SetSingle<IAssembliesResolver>((IAssembliesResolver) new DefaultAssembliesResolver());
this.SetSingle<IBodyModelValidator>((IBodyModelValidator) new DefaultBodyModelValidator());
this.SetSingle<IContentNegotiator>((IContentNegotiator) new DefaultContentNegotiator());
this.SetSingle<IDocumentationProvider>((IDocumentationProvider) null);
this.SetMultiple<IFilterProvider>((IFilterProvider) new ConfigurationFilterProvider(), (IFilterProvider) new ActionDescriptorFilterProvider());
this.SetSingle<IHostBufferPolicySelector>((IHostBufferPolicySelector) null);
this.SetSingle<IHttpActionInvoker>((IHttpActionInvoker) new ApiControllerActionInvoker());
this.SetSingle<IHttpActionSelector>((IHttpActionSelector) new ApiControllerActionSelector());
this.SetSingle<IHttpControllerActivator>((IHttpControllerActivator) new DefaultHttpControllerActivator());
this.SetSingle<IHttpControllerSelector>((IHttpControllerSelector) new DefaultHttpControllerSelector(configuration));
this.SetSingle<IHttpControllerTypeResolver>((IHttpControllerTypeResolver) new DefaultHttpControllerTypeResolver());
this.SetSingle<ITraceManager>((ITraceManager) new TraceManager());
this.SetSingle<ITraceWriter>((ITraceWriter) null);
this.SetMultiple<ModelBinderProvider>((ModelBinderProvider) new TypeConverterModelBinderProvider(), (ModelBinderProvider) new TypeMatchModelBinderProvider(), (ModelBinderProvider) new KeyValuePairModelBinderProvider(), (ModelBinderProvider) new ComplexModelDtoModelBinderProvider(), (ModelBinderProvider) new ArrayModelBinderProvider(), (ModelBinderProvider) new DictionaryModelBinderProvider(), (ModelBinderProvider) new CollectionModelBinderProvider(), (ModelBinderProvider) new MutableObjectModelBinderProvider());
this.SetSingle<ModelMetadataProvider>((ModelMetadataProvider) new DataAnnotationsModelMetadataProvider());
this.SetMultiple<ModelValidatorProvider>((ModelValidatorProvider) new DataAnnotationsModelValidatorProvider(), (ModelValidatorProvider) new DataMemberModelValidatorProvider());
this.SetMultiple<ValueProviderFactory>((ValueProviderFactory) new QueryStringValueProviderFactory(), (ValueProviderFactory) new RouteDataValueProviderFactory());
this.SetSingle<IModelValidatorCache>((IModelValidatorCache) new ModelValidatorCache(new Lazy<IEnumerable<ModelValidatorProvider>>((Func<IEnumerable<ModelValidatorProvider>>) (() => ServicesExtensions.GetModelValidatorProviders((ServicesContainer) this)))));
this.SetSingle<IExceptionHandler>((IExceptionHandler) new DefaultExceptionHandler());
this.SetMultiple<IExceptionLogger>();
this._serviceTypesSingle = new HashSet<Type>((IEnumerable<Type>) this._defaultServicesSingle.Keys);
this._serviceTypesMulti = new HashSet<Type>((IEnumerable<Type>) this._defaultServicesMulti.Keys);
this.ResetCache();
}
您可以查看Web API团队的以下示例：
http://aspnet.codeplex.com/SourceControl/latest#Samples/WebApi/Elmah/ReadMe.txt