ASP.NET Core is a popular web development framework that provides developers with a set of tools and libraries for building modern web applications. Handling errors is an essential part of any web application development, and ASP.NET Core provides developers with several ways to handle errors in their web APIs. In this article, we will take a deep dive into how to handle errors in ASP.NET Core web APIs.
Introduction
Errors are an inevitable part of any software development process. No matter how well you write your code, there will always be the possibility of errors occurring in your application. Handling errors in a web API is essential for providing a good user experience and preventing users from encountering confusing error messages.
ASP.NET Core provides developers with several ways to handle errors in their web APIs. In this article, we will explore these methods, including using the Developer Exception Page, Exception Handler Middleware, and custom middleware for global error handling.
The Developer Exception Page
The Developer Exception Page is a built-in middleware in ASP.NET Core that provides detailed stack traces for server errors. It captures synchronous and asynchronous exceptions from the HTTP pipeline and generates error responses. The Developer Exception Page is an excellent tool for developers to debug their applications during development.
To use the Developer Exception Page, you need to enable it in your application's Startup.cs class. You can do this by adding the following code to the Configure method:
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
This code checks if the environment is set to development and adds the Developer Exception Page middleware to the HTTP pipeline. When an unhandled exception occurs, the Developer Exception Page will capture it and generate a detailed stack trace.
Exception Handler Middleware
The Exception Handler Middleware is another built-in middleware in ASP.NET Core that provides a more structured way of handling errors. It catches exceptions that occur after the HTTP pipeline has been executed and generates an error response.
To use the Exception Handler Middleware, you need to add it to the HTTP pipeline in your application's Startup.cs class. You can do this by adding the following code to the Configure method:
if (!env.IsDevelopment())
{
app.UseExceptionHandler("/error");
}
This code checks if the environment is not set to development and adds the Exception Handler Middleware to the HTTP pipeline. If an unhandled exception occurs, the middleware will catch it and redirect the request to the /error endpoint.
You can then create an action method to handle the error response. For example:
[Route("/error")]
public IActionResult HandleError()
{
return Problem();
}
This code creates an action method that returns a Problem object, which is a standardized error payload that complies with the RFC 7807 specification.
Custom Middleware for Global Error Handling
While the Developer Exception Page and Exception Handler Middleware are useful tools for handling errors, they are limited to handling errors within the HTTP pipeline. If you want to handle errors globally, you can create custom middleware that intercepts all requests and responses.
To create custom middleware for global error handling, you need to create a class that implements the IMiddleware interface. This interface contains a single method, InvokeAsync, which is called for every request that passes through the middleware.
public class ErrorHandlingMiddleware : IMiddleware
{
private readonly ILogger _logger;
public ErrorHandlingMiddleware(ILogger<ErrorHandlingMiddleware> logger)
{
_logger = logger;
}
public async Task InvokeAsync(HttpContext context, RequestDelegate next)
{
try
{
await next(context);
}
catch (Exception ex)
{
_logger.LogError(ex, "An unhandled exception has occurred.");
context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
context.Response.ContentType = "text/plain";
await context.Response.WriteAsync("An error has occurred. Please try again later.");
}
}
}
This code creates a custom middleware class that intercepts all requests and responses. If an unhandled exception occurs, the middleware will catch it and log the error message. It will then return a plain-text error message to the client.
To add the custom middleware to the HTTP pipeline, you need to add the following code to your application's Startup.cs class:
app.UseMiddleware<ErrorHandlingMiddleware>();
This code adds the custom middleware to the HTTP pipeline, and it will intercept all requests and responses.
Conclusion
Handling errors is an essential part of any web application development, and ASP.NET Core provides developers with several ways to handle errors in their web APIs. The Developer Exception Page, Exception Handler Middleware, and custom middleware for global error handling are all useful tools for handling errors in ASP.NET Core web APIs.
By using these tools, you can provide a better user experience for your users and make it easier to debug your application during development. Whether you choose to use the built-in middleware or create your custom middleware, handling errors is an essential part of building a robust and reliable web API.
