C#

C# Programming Language

C# – Ignore the Nullable CS8618 warning in DTO classes

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When you have the Nullable Reference Types feature (Nullable for short) enabled, one of the warnings you’ll run into is the following: CS8618 Non-nullable property X must contain a non-null value when exiting constructor. This warning doesn’t make sense in a very common scenario: You have a DTO class with a non-nullable reference type, such … Read more

C# – How to treat warnings like errors

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Warnings are easy to ignore and forget about, which isn’t good. They point out potential problems that you might want to fix. To make it easier to pay attention to warnings, you can treat them like errors. You can choose which warnings to treat like errors by using settings in the project file. There are … Read more

C# – Nullable Reference Types feature basics

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The main purpose of the Nullable Reference Types (NRT) feature is to help prevent NullReferenceExceptions by showing you compiler warnings. You can make a reference type nullable (ex: Movie? movie) or non-nullable (ex: Movie movie). This allows you to indicate how you plan on using these references. The compiler uses this info while analyzing actual … Read more

C# – How to use JsonNode to read, write, and modify JSON

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When you don’t want to create classes for JSON (de)serialization, one option is to use JsonNode. This allows you work with JSON as a mutable DOM that consists of JsonNode objects (JsonObject, JsonArray, JsonValue). You can use it to read, write, and modify JSON. Here’s an example. Let’s say you have the following JSON that … Read more

C# – Filter a dictionary

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The simplest way to filter a dictionary is by using the Linq Where() + ToDictionary() methods. Here’s an example: Note: You can use the Dictionary constructor (new Dictionary<string, int>(filterList)) instead of ToDictionary() if you prefer. This produces a new dictionary with the filtered item: Where() produces a list (actually an IEnumerable) of KeyValuePair objects. Most … Read more

C# – Change a dictionary’s values in a foreach loop

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In .NET 5 and above, you can directly change a dictionary’s values in a foreach loop. Here’s an example: This outputs the following: You couldn’t do this before .NET 5, because it would invalidate the enumerator and throw an exception: InvalidOperationException: Collection was modified; enumeration operation my not execute. Instead, you’d have to make the … Read more

C# – Get a time zone’s display name with the current date’s UTC offset

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A time zone’s UTC offset can change based on the time of year due to daylight savings time. One problem with the TimeZoneInfo class is that TimeZoneInfo.DisplayName always shows the base UTC offset, even if the current date is in daylight savings time. This may be confusing to users (and this is the same thing … Read more

C# – How to use TimeZoneInfo

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Time zones are complicated and their rules can change, so it makes sense to use a library when you’re dealing with them. One option in .NET is to use the built-in TimeZoneInfo class. Here’s an example of using TimeZoneInfo to get the local system’s time zone: This outputs: Note: The display name always show the … Read more

C# – Get the current date and time

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Here’s an example of how to get the current date/time: This outputs the current local date/time: Note: By default, it uses the current culture’s format (from the OS). This is showing the US date format – MM/dd/yyyy. DateTime.Now is the local date/time from the system where the code is executing. Keep that in mind if … Read more