How to handle exceptions globally in a .NET Core API using middleware?

Question

Aryan Kumar · Answer

To handle exceptions globally in a .NET Core API using middleware, you can use the UseExceptionHandler middleware. The UseExceptionHandler middleware catches all unhandled exceptions and redirects them to a handler that you specify.

To use the UseExceptionHandler middleware, you need to add it to the middleware pipeline in your Startup class. The following code shows how to do this:

C#

public void Configure(IApplicationBuilder app) {
  app.UseExceptionHandler("/error");
  // Other middleware...
}

The /error route is the route that the UseExceptionHandler middleware will redirect to when it catches an unhandled exception. You can customize the route by passing a different value to the UseExceptionHandler method.

The handler that you specify for the UseExceptionHandler middleware is responsible for handling the unhandled exceptions. The following code shows a simple example of a handler that logs the exception to the console:

C#

app.UseExceptionHandler("/error")
  .Run(async (context, exception) => {
    context.Response.StatusCode = 500;
    context.Response.ContentType = "application/json";
    context.Response.WriteAsync(JsonConvert.SerializeObject(exception));
  });

This handler sets the response status code to 500 (Internal Server Error) and the response content type to "application/json". The handler then serializes the exception object to JSON and writes it to the response stream.

You can customize the handler to do whatever you want with the unhandled exception. For example, you could send an email notification to the developers, or you could retry the operation a few seconds later.

By using the UseExceptionHandler middleware, you can ensure that all unhandled exceptions are handled gracefully in your .NET Core API. This will help you to improve the reliability of your application and provide a better experience for your users.

Here are some additional tips for handling exceptions globally in a .NET Core API using middleware:

Use a try-catch block to handle exceptions in your code. This will allow you to catch and handle exceptions before they reach the UseExceptionHandler middleware.
Log the exception to a file or database. This will help you to track down the cause of the error.
Retry the operation if the exception is transient. For example, if the database is unavailable, you can retry the operation a few seconds later.

By following these tips, you can ensure that your .NET Core API can handle exceptions gracefully and provide a good user experience.

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