如何在 .NET Core 中捕获异常并使用状态代码进行响应 [英] How to catch an exception and respond with a status code in .NET Core

问题描述

我正在运行一个 .Net Core Web API 项目.我有一个启动文件(如下).在 Startup.ConfigureServices(...) 方法中，我添加了一个创建 IFoo 实例的工厂方法.我想捕获 IFooFactory 抛出的任何异常并返回带有状态代码的更好的错误消息.目前，我收到 500 错误和异常消息.有人可以帮忙吗?

I am running a .Net Core Web API project. I have a startup file (below). In the Startup.ConfigureServices(...) method, I add a factory method that creates an instance of IFoo. I want to catch any exceptions that the IFooFactory throws and return a better error message with a status code. At the moment I getting a 500 Error with the exception Message. Can anyone help?

public interface IFooFactory
{
    IFoo Create();  
}

public class FooFactory : IFooFactory
{
    IFoo Create()
    {
        throw new Exception("Catch Me!");
    }
}

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddScoped<IFooFactory,FooFactory>();
        services.AddScoped(serviceProvider => {
            IFooFactory fooFactory = serviceProvider.GetService<IFooFactory>();
            return fooFactory.Create(); // <== Throws Exception
        });
    }
}

推荐答案

所以当我以两种不同的方式阅读问题时，我发布了两个不同的答案 - 大量删除/取消删除/编辑 - 不确定哪一个真正回答了您的问题问题:

So I've posted two different answers as I read the question in two different ways - lots of deleting/undeleting/editing - not sure which one actually answers your question:

要找出应用启动时出了什么问题并且根本无法运行，请尝试以下操作:

在Startup中使用开发者异常页面:

Use the developer exception page in Startup:

public void Configure(IApplicationBuilder app, IHostingEnvironment env,
                           ILoggerFactory loggerFactory)
{
    app.UseDeveloperExceptionPage();
}

在 Program 类中:

public static void Main(string[] args)
{
    var host = new WebHostBuilder()
        .UseKestrel()
        .UseContentRoot(Directory.GetCurrentDirectory())
        .UseIISIntegration()
        .UseStartup<Startup>()
        .UseApplicationInsights()
        .CaptureStartupErrors(true) // useful for debugging
        .UseSetting("detailedErrors", "true") // what it says on the tin
        .Build();

    host.Run();
}

如果你想在 api 正常工作时处理偶尔的异常，那么你可以使用一些中间件:

public class ExceptionsMiddleware
{
    private readonly RequestDelegate _next;

    /// <summary>
    /// Handles exceptions
    /// </summary>
    /// <param name="next">The next piece of middleware after this one</param>
    public ExceptionsMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    /// <summary>
    /// The method to run in the piepline
    /// </summary>
    /// <param name="context">The current context</param>
    /// <returns>As task which is running the action</returns>
    public async Task Invoke(HttpContext context)
    {
        try
        {
            await _next.Invoke(context);
        }
        catch(Exception ex)
        {
            // Apply some logic based on the exception
            // Maybe log it as well - you can use DI in
            // the constructor to inject a logging service

            context.Response.StatusCode = //Your choice of code
            await context.Response.WriteAsync("Your message");
        }
    }
}

这有一个问题"——如果响应头已经发送，你就不能写状态码.

您使用 Configure 方法在 Startup 类中配置中间件:

You configure the middleware in the Startup class using the Configure method:

public void Configure(IApplicationBuilder app, IHostingEnvironment env,
                           ILoggerFactory loggerFactory)
{
    app.UseMiddleware<ExceptionsMiddleware>();
}

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