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Dictionaries have keys mapped to values, which enables you to efficiently lookup values by key. But you can also do a reverse lookup: get the key associated with a value. The simplest option is to use FirstOrDefault(), but that’s only a good idea if you know the value exists for sure. Instead, the best option … Read more
Dictionaries contain key/value pairs. When you want to remove one or more items from a dictionary, you can use one of the following methods: I’ll show examples below. Remove item by key Use Dictionary.Remove() to remove an item based on its key. If the key exists, it removes the key/value pair from the dictionary and … Read more
There are two ways to receive CSV data in a web API: In this article, I’ll show examples of both of these approaches. I’ll be using the CsvHelper library to parse CSV data into model objects and then do model validation. Note: To use CsvHelper, install the CsvHelper package (Install-Package CsvHelper). Or use whichever parser … Read more
Deconstructing an object means assigning its properties to several variables with a one-liner using deconstruction assignment syntax (also referred to as destructuring or unpacking). Here’s an example of deconstructing an object: This outputs the following: Several built-in types already support deconstruction – such as tuples, dictionary (KeyValuePair), and records. You can enable deconstruction for any … Read more
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
You can use the Description attribute to describe types and type members (properties, methods). One of the most common use cases is providing a user-friendly string for enum values. Here’s an example of using the Description attribute with an enum: To read the Description attribute, use reflection and do the following steps: This can be … Read more
When you want to exclude a method from showing up in the stack trace, you can apply the StackTraceHidden attribute to the method: Note: This attribute was added in .NET 6. You can apply StackTraceHidden to a class to hide all of its methods from the stack trace: Use StackTraceHidden with throw helper methods StackTraceHidden … Read more
Here’s how to round a DateTime up to the nearest 30 minutes: When the time is 3:38 pm, it rounds to 4:00 pm. When it’s 5:03 pm, it rounds to 5:30 pm. When it’s exactly 2:00 pm, it’ll round up to 2:30 pm (note: see the What if you’re at the start of a 30 … Read more
Query strings start with ‘?’ and have one or more key-value pairs separated by ‘&’. All characters except a-z, A-Z, 0-9 have to be encoded, including Unicode characters. When you use HttpClient, it automatically encodes the URI for you (internally, it delegates this task to the Uri class). This means when you include a query … Read more
Here’s the simplest way to efficiently trim a UTF-8 string to the specified number of bytes: A UTF-8 string can have a mix of characters between 1 to 4 bytes. When you only take part of the byte array, you may end up cutting multi-byte chars in half, which then get replaced with the replacement … Read more
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 anonymous type parameter. For example, let’s say you’re trying to unit test the following method: To unit test this, you … Read more
There are two ways add request headers when using HttpClient: 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 included in all requests and the value won’t change. To add this request … Read more
In a consumer/producer scenario, there are many reasons why you might want the consumer to read a batch of items. Maybe you’re bulk inserting into the database, or sending a payload with HttpClient. Sending lots of individual items over the network can be costly, and waiting for a full batch of items before sending is … Read more
System.Net.Http.Json provides extension methods that simplify getting and sending JSON with HttpClient. Internally, it uses System.Text.Json for serialization. What if you want to use Newtonsoft instead of System.Text.Json? You can use the following extension methods for that: These are modeled off of the extension methods in System.Net.Http.Json. HttpClient is used to fetch the JSON content … Read more
Update Jan-2025: Starting in version 8+, someone decided to add very expensive commercial licensing to FluentAssertions. I would advise you to stick with version 7 and below or use an alternative (like Shouldly). You can check out the discussions about this in the GitHub repo. FluentAssertions is a library that improves unit tests by providing … Read more
Normally when you want to join strings using a separator, you’d use string.Join(). However, the problem with string.Join() is it doesn’t ignore nulls or empty strings. Take a look at the following examples: If you want to filter out nulls and empty strings, you can filter the list of strings yourself and pass it into … Read more
SqlDataReader returns a DBNull object when a column is null. This isn’t the same as a C# null. You can check if the column is null by comparing it with DBNull.Value or by using SqlDataReader.IsDBNull(). Here’s an example showing these two ways of checking if a column is null: After checking if the column is … Read more
XML documentation comments serve two purposes: In this article I’ll show how to automatically generate an XML documentation file and how to include it in a nuget package. 1 – Write the XML documentation comments in your code I have a method called MergeInPlace() (which merges two dictionaries in-place). To explain what this is doing … Read more
When you merge two dictionaries, you can either merge them in-place, or create a new dictionary and copy the values over to it. The following extension method does an in-place merge of two dictionaries. It loops through items in the right dictionary, adding them to the left dictionary. When duplicate keys exist, it’s keeping the … Read more
This article shows code for converting a hex string to a byte array, unit tests, and a speed comparison. First, this diagram shows the algorithm for converting a hex string to a byte array. To convert a hex string to a byte array, you need to loop through the hex string and convert two characters … Read more
Problem When you call .First() on an empty IEnumerable, you get the following exception: System.InvalidOperationException: Sequence contains no elements Solution Option 1 – Use .FirstOrDefault() instead of .First() When the IEnumerable is empty, .FirstOrDefault() returns the default value for the type. For reference types this returns null. For value types this returns 0 or that … Read more
Attributes are used to store additional info about a class/method/property. The attributes are read at runtime and used to change the program’s behavior. Here are a few examples of commonly used built-in attributes: In general, you should try to use built-in attributes when possible. When it makes sense, you can create your own custom attribute. … Read more