task-delay

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

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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# – Configuring HttpClient connection keep-alive

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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# – Circuit breaker with Polly

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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

Logging to the database with ASP.NET Core

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I was reading about logging in ASP.NET when I came across this statement about logging to the database: When logging to SQL Server, don’t do so directly. Instead, add log messages to an in-memory queue and have a background worker dequeue and insert data to SQL Server. Paraphrased from Microsoft – No asynchronous logger methods … Read more

C# – Async/await with a Func delegate

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To make a Func delegate awaitable, you have to make its out parameter a Task, like this: This Func accepts an int parameter and returns a Task. Since it returns a Task, it can be awaited. Notice that this isn’t returning a value. Normally you’d use an Action delegate if you didn’t want to return … Read more

How to use toxiproxy to simulate web API error scenarios

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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

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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

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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

ASP.NET – Async SSE endpoint

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Server-Sent Events (SSE) allow a client to subscribe to messages on a server. The server pushes new messages to the client as they happen. This is an alternative to the client polling the server for new messages. In this article I’ll show how to implement the messaging system shown in the diagram below. This uses … Read more

C# – Async Main

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The Async Main feature was added in C# 7.1 and works with all overloads of the Main() method. To make the Main() method async, add async Task to the method signature, like this: This is syntax sugar that compiles down to calling GetAwaiter().GetResult() on whatever you’re awaiting. In other words, it’s equivalent to doing the … Read more

C# – How to consume an SSE endpoint with HttpClient

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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# – Use SemaphoreSlim for throttling threads

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When you have multiple threads trying to do work at the same time, and you want to throttle how many of them are actually executing (such as when you’re sending concurrent requests with HttpClient), you can use SemaphoreSlim. Example – a busy grocery store Grocery stores have a limited number of checkout lanes open. Let’s … Read more

C# – Example of using BlockingCollection

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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()

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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

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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