Global Exception Handling In Asp.net Core Web API

Introduction

In the context of ASP.NET Core Web API (or any web application framework), global exception handling involves catching exceptions that occur during the processing of requests and returning appropriate error responses to the clients. Instead of allowing exceptions to propagate to the top level and exposing technical details to the end-users, global exception handling can convert those exceptions into more informative and standardized error messages in a format such as JSON or XML.

Key benefits of using global exception handling

1. Consistent Error Responses: Global exception handling ensures that all exceptions are handled and translated into a consistent format, making it easier for clients to understand and handle errors uniformly.
2. Improved User Experience: Instead of displaying cryptic error messages or stack traces, global exception handling can present user-friendly messages that explain the error in a human-readable way.
3. Application Resilience: By handling exceptions at a central level, the application can gracefully recover from errors and continue functioning without crashing.
4. Logging and Monitoring: Global exception handling allows you to log exception details, helping you to monitor and diagnose application issues in production environments.
5. Security: By not exposing low-level technical details of exceptions to users, you can prevent potential security vulnerabilities.

In ASP.NET Core, global exception handling is typically implemented using middleware. Middleware is a pipeline component that can inspect, modify, or terminate incoming requests and outgoing responses. You can create custom middleware to handle exceptions and register it in the application pipeline.

implementation of  global exception handling

A common approach to implementing global exception handling involves,

1. Creating a custom middleware that catches exceptions and generates appropriate error responses.
2. Registering the custom middleware in the ASP.NET Core application pipeline, ensuring it's invoked for all requests.
3. Handling various types of exceptions (e.g., application-specific exceptions, system-level exceptions) and returning appropriate status codes and messages.

Global exception handling can also work in conjunction with logging frameworks, such as Serilog or NLog, to log exception details for better monitoring and debugging.

However, it's essential to use global exception handling judiciously. Some exceptions may indicate unrecoverable errors or security vulnerabilities, and handling them globally might not be appropriate. In such cases, you may need to let those exceptions propagate up to the top-level error handler or handle them specifically in certain parts of your application.

Remember that while global exception handling can provide a safety net for unhandled exceptions, it is also crucial to design your application in a way that minimizes the occurrence of exceptions and to thoroughly test your code to catch any potential issues early in the development process.

Complete Implementation With Example

Step 1. Create a new ASP.NET Core Web API Project

Start by creating a new ASP.NET Core Web API project. You can do this using the command-line interface (CLI) or by using Visual Studio.

Step 2. Install the required NuGet packages

Install the following NuGet packages to handle global exception handling:

dotnet add package Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore
dotnet add package Microsoft.AspNetCore.Mvc.NewtonsoftJson

Step 3. Create a custom exception class 

You can create a custom exception class to represent specific application-level exceptions. This can be useful for adding more context to the errors.

Author sardar mudassar ali khan
public class CustomException: Exception
{
    public CustomException(string message) : base(message)
    {
    }

    // We can add some properties here for Customized Messages 
}

Step 4. Implement global exception-handling middleware

Create a new middleware class to handle global exceptions. The middleware will catch unhandled exceptions and convert them into appropriate HTTP responses.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Diagnostics;
using Microsoft.AspNetCore.Http;
using System.Net;

Author sardar mudassar ali khan
public class GlobalExceptionMiddleware
{
    public async Task InvokeAsync(HttpContext context, Func<Task> next)
    {
        try
        {
            await next();
        }
        catch (Exception ex)
        {
            await HandleExceptionAsync(context, ex);
        }
    }

    private static Task HandleExceptionAsync(HttpContext context, Exception ex)
    {
        context.Response.ContentType = "application/json";
        context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;

        var response = new
        {
            error = new
            {
                message = "An error occurred while processing your request.",
                details = ex.Message 
            }
        };

        return context.Response.WriteAsync(JsonConvert.SerializeObject(response));
    }
}

Step 5. Register the global exception handling middleware in the Startup.cs file

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

Author sardar mudassar ali khan
public class Startup
{

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers().AddNewtonsoftJson();
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/error");
            endpoint if needed
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseRouting();

        app.UseMiddleware<GlobalExceptionMiddleware>();

        app.UseAuthorization();
        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

Conclusion

Global exception handling is essential to software development, particularly in web applications like ASP.NET Core Web API. By implementing global exception handling, we can catch and manage exceptions that occur during the processing of requests at a centralized level. This approach offers several benefits, including providing consistent and user-friendly error responses, improving the application's resilience, and enhancing the overall user experience.