C#

C# Programming Language

C# – How to match an anonymous type parameter in a mocked method

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When an anonymous type is defined in one assembly, it won’t match an anonymous type defined in another assembly. This causes problems when you’re unit testing and trying to mock a method that has an an anonymous type parameter. For example, let’s say you’re trying to unit test the following method: To unit test this, … Read more

C# – Add or overwrite a value in ConcurrentDictionary

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The simplest way to add or overwrite a value in a ConcurrentDictionary is to use the indexer: If the key doesn’t exist, this adds it. If the key exists, this overwrites it. The indexer is thread-safe. The indexer is the simplest way to unconditionally add / overwrite a value. Sometimes you’ll want to use other … Read more

ASP.NET Core – Get posted form data in an API Controller

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To get posted form data in an API Controller (using the [ApiController] attribute) in ASP.NET Core, use parameters with the [FromForm] attribute. A request to this endpoint would look like this: The form data is a string of key-value pairs (ex: location=United+States). The framework tries to map the form data to parameters by matching the … Read more

C# – Convert a list to a dictionary

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The simplest way to convert a list to a dictionary is to use the Linq ToDictionary() method: This loops through the list and uses the key/element selector lambdas you passed in to build the dictionary. In this article, I’ll go into details about how to use ToDictionary() and show how to deal with duplicate keys. … Read more

C# – Unit testing code that does File IO

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If your code does File IO, such as reading text from a file, then it’s dependent on the file system. This is an external dependency. In order to make the unit tests fast and reliable, you can mock out the external dependencies. To mock out the file system dependency, you can wrap the File IO … Read more

Get SQL Server query results as JSON

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The simplest way to get query results as JSON is to use FOR JSON PATH in the query (note: this was added in SQL Server 2016): It returns the results as a single JSON string with one JSON object per row: Note: SQL Server returns the JSON without indenting. All examples in this article show … Read more

C# – Select distinct objects based on a property

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There are three ways to select distinct objects based on a property using Linq: These select one movie per year: GroupBy() is the simplest because it doesn’t require any additional code. Distinct() is faster but it’s more complicated. DistinctBy() is the fastest and simplest, but requires the most code (it requires .NET 6 or getting … Read more

C# – Using reflection to get properties

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You can get a list of a type’s properties using reflection, like this: Note: If you have an object, use movie.GetType().GetProperties() instead. This outputs the following: When you use GetProperties(), it returns a list of PropertyInfo objects. This gives you access the property’s definition (name, type, etc…) and allows you to get and modify its … Read more

C# – How to add request headers when using HttpClient

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There are two ways add request headers when using HttpClient: Add headers for all requests using HttpClient.DefaultRequestHeaders. Add headers per request using HttpRequestMessage.Headers. In this article, I’ll show examples of both ways to add request headers. Add an unchanging header for all requests Let’s say you’re adding an API Key header. It needs to be … Read more

Comparing performance with Benchmark.NET graphs

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The following graph compares the execution time of three sort implementations ran against varying input sizes (1k, 10k, 100k): This graph was generated using Benchmark.NET, which I’ll show how to use in this article. I’ll be comparing the performance of multithreaded quicksort implementations (with the non-threaded Array.Sort() as a baseline). Create console app and reference … Read more