ASP.NET Core – Control the graceful shutdown time for background services

ASP.NET Core gives you a chance to gracefully shutdown your background services (such as cleaning up and/or finishing in-progress work). By default, you’re given a grand total of 5 seconds to shutdown all background services. If you need more time than this, there are a few ways to control the graceful shutdown time, which I’ll … Read more

C# – TimeZoneInfo with current UTC offset

TimeZoneInfo always shows the base UTC offset. This can be confusing because the UTC offset can change based on the date (due to daylight savings rules). Here’s an example showing DateTimeOffset and TimeZoneInfo with different offsets: You can get a date’s UTC offset from DateTimeOffset and combine it with TimeZoneInfo.DisplayName. This approach is implemented in … Read more

C# – Deserialize JSON as a stream

Here’s an example of deserializing JSON from a file as a stream with System.Text.Json: Stream deserialization has three main benefits: In this article, I’ll go into details about these benefits and show a few other stream serialization scenarios. Benefits of deserializing as a stream Performance There are two ways to deserialize JSON: Deserializing a stream … Read more

WinForms – Date and time input

When you need to let the user select a date and/or time of day, you can use the DateTimePicker control: You can set the control properties in the UI or programmatically: If you don’t set an initial value, it’ll default to DateTime.Now (at the time the code is executed). The value the user picked is … Read more

C# – Using top-level statements

The top-level statements feature makes the Main() method implicit. This feature was added in C# 9 (.NET 5) with the purpose of decluttering a project’s entry point. Here’s what a console app looks like using a top-level statement: The compiler generates the Main() method implicitly from the top-level statements. The code above is functionally equivalent … Read more

C# – Configuring HttpClient connection keep-alive

When you use a single instance of HttpClient to send requests, it keeps connections open in order to speed up future requests. By default, idle connections are closed after 2 minutes, and otherwise will be kept open forever (in theory). In reality, the connection can be closed by the server-side (or other external factors) regardless … Read more

C# – Disposing the request HttpContent when using HttpClient

In versions before .NET Core 3.0 (including .NET Framework), HttpClient disposes the request HttpContent object for you. This is surprising default behavior (a violation of the principle of least surprise for sure). This causes multiple problems, but one of the main problems is it prevents you from reusing the HttpContent object (you’re greeted with an … Read more

C# – Circuit breaker with Polly

In an electrical system, a circuit breaker detects electrical problems and opens the circuit, which blocks electricity from flowing. To get electricity flowing again, you have to close the circuit. The same approach can be implemented in software when you’re sending requests to an external service. This is especially important when you’re sending lots of … Read more

C# – How to use Polly to do retries

Whenever you’re dealing with code that can run into transient errors, it’s a good idea to implement retries. Transient errors, by definition, are temporary and subsequent attempts should succeed. When you retry with a delay, it means you think the the transient error will go away by itself after a short period of time. When … Read more

How to do retries in EF Core

EF Core has built-in retry functionality. To use it, you can call options.EnableRetryOnFailure(), like this: The retry logic is contained in execution strategy classes. The above code is using the default execution strategy class (SqlServerRetryingExecutionStrategy). When you execute a query, it goes through the execution strategy class. It executes the query and checks for transient … Read more

C# – How to change the HttpClient timeout per request

When you’re using the same HttpClient instance to send multiple requests, and you want to change the timeout per request, you can pass in a CancellationToken, like this: You can’t change HttpClient.Timeout after the instance has been used. You have to pass in a CancellationToken instead. There are other key points to know when trying … Read more

How to use toxiproxy to simulate web API error scenarios

When you have code that calls an endpoint, you need to make sure it’s resilient and can handle error scenarios, such as timeouts. One way to prove your code is resilient is by using toxiproxy to simulate bad behavior. Toxiproxy sits between your client code and the endpoint. It receives requests from your client, applies … Read more

C# – Conditionally catch exceptions with filtering

You can use exception filtering to conditionally catch exceptions, like this: Note: This feature was added in C# 6. Any SqlException that doesn’t meet the condition specified in the when clause will not be caught. Previously, without exception filtering, you’d have to handle that scenario in the catch block and rethrow, like this: Exception filtering … Read more

How to use BackgroundService in ASP.NET Core

You can use a hosted BackgroundService in ASP.NET Core for two purposes: In this article, I’ll show how to create and register a hosted BackgroundService. In this example, it periodically pings a URL and logs the results. 1 – Subclass BackgroundService The first step is to subclass BackgroundService: In this example, we’ll create a background … Read more

C# – How to consume an SSE endpoint with HttpClient

Server-Sent Events (SSE) allow a client to subscribe to messages from the server. It creates a one-way stream from the server to the client. When the server has new messages for the client, it writes them to the stream. This is an alternative to the client polling the server for updates. Use the following to … Read more

C# – Example of using BlockingCollection

The BlockingCollection class is a blocking concurrent queue. It provides an implementation of the producer-consumer pattern. There are two parts to this pattern: BlockingCollection is thread-safe, which means it’s designed to be used by many threads at once. Here’s an example of using BlockingCollection with one consumer and two producers: Note: BlockingCollection.IsCompleted means the queue … Read more

How to set a timeout for TcpClient.ConnectAsync()

TcpClient has no direct way to set the connection timeout. It doesn’t have any parameters that allow you to control it, and SendTimeout / ReceiveTimeout don’t apply to the initial connection. The way I control the connection timeout is by awaiting a Task.WhenAny() with TcpClient.ConnectAsync() and Task.Delay(). Task.WhenAny() returns when any of the tasks complete. … Read more

How to update UI from another thread

I often need to be able to run multiple threads and update the UI based on the results. For example, I may need to execute GET requests to 10 different endpoints concurrently, and then report their results in a datagrid as they come back. The problem is you can’t just update the UI from any … Read more