如何在 .NET Core 中捕获异常并使用状态代码进行响应

Question

我是运行 .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 抛出的任何异常和 return 带有状态代码的更好的错误消息。目前我收到 500 错误消息异常。有人可以帮忙吗？

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
        });
    }
}

Answer 1

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 - 很多 deleting/undeleting/editing - 不确定哪一个真正回答了你的问题：

要弄清楚应用程序启动时出现什么问题并且根本无法运行，请尝试以下操作：

在Startup中使用开发者例外页面：

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

并且在 Program class:

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");
        }
    }
}

有一个'gotcha' - 如果响应头已经发送，你不能写状态码。

您在 Startup class 中使用 Configure 方法配置中间件：

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

如何在 .NET Core 中捕获异常并使用状态代码进行响应

How to catch an exception and respond with a status code in .NET Core

.net

c#

dependency-injection

exception-handling

.net-core