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The simplest way to convert a dictionary to a list is by using the Linq ToList() method, like this: When used on a dictionary, ToList() returns a list of KeyValuePair objects. This example outputs the following: Dictionary keys to list If you want a list of the dictionary’s keys, use ToList() on Dictionary.Keys, like this: … 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
The simplest (and most efficient) way to remove duplicates from a list is by iterating, keeping track of items you’ve seen with a HashSet, and discarding items you’ve already seen. I’ll show four ways to implement this O(n) algorithm. At the end, I’ll explain a few inefficient approaches to avoid. Remove duplicates with ToHashSet() and … Read more
You can convert a list of strings to a list of integers by using int.Parse() on all of the strings. There are two simple ways to do this: I’ll show examples of these using these methods and then explain how to handle parsing exceptions. Option 1 – Use List.ConvertAll() Here’s an example of how to … Read more
The simplest way to convert an array to a list is with the ToList() Linq method: This outputs the following: Besides using ToList(), you can also use the list constructor or AddRange(). Before I show those, I’ll explain why you’d want to use these special methods instead of just adding items individually to a new … Read more
When you need to sort a list, you don’t need to reinvent the wheel. You can use one of these three built-in methods for sorting a list: In this article, I’ll show examples of using these three approaches for sorting a list. Sort a list with OrderBy() (Linq) The OrderBy() Linq method generates an IOrderedEnumerable … Read more
Here’s an example of how to initialize a list of named tuples: This creates a list of named value tuples (ValueTuple<string, int>) using list initializer syntax and then loops through the tuples. I suggest always using named value tuples (not System.Tuple). This outputs the following: I’ll now show how to add to the list of … Read more
Let’s say you want to parse a comma-separated string into a list of integers. For example, you have “1,2,3” and you want to parse it into [1,2,3]. This is different from parsing CSV with rows of comma-separated values. This is more straightforward. You can use string.Split(“,”) to get the individual string values and then convert … Read more
In this article, I’ll show how to parse a CSV file manually and with a parser library (CsvHelper). Let’s say you have the following CSV file: To manually parse this, read the file line by line and split each line with a comma. This gives you a string array containing the fields that you can … Read more
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
In .NET 5 and above, you can loop through a dictionary and directly change its values. 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