foreach

C# – Copy a dictionary

by

The simplest way to make a copy of a dictionary is to use the copy constructor. You pass the dictionary you want to copy to the new dictionary’s constructor, like this: Note: If you’re using a non-default comparer, you’ll want to pass it to the copy constructor (i.e. new Dictionary(d, d.Comparer)). The copy constructor handles … Read more

C# – Convert a dictionary to a list

by

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

C# – Deserialize JSON to a dictionary

by

I’ll show examples of how to deserialize JSON to dictionaries in different scenarios. Deserializing to Dictionary<string, string> When your JSON object has properties with simple string values (as opposed to nested objects), you can deserialize to Dictionary<string, string>. Here’s an example. Consider the following simple JSON object: Note: In all examples, I’ll show the pretty-printed … Read more

C# – Find duplicate values in a dictionary

by

Dictionaries contain key/value pairs. The keys must be unique, but the values can be repeated many times. When you want to find duplicate values, the simplest option is to use Linq methods GroupBy() and Where(), like this: Note: I initialized the dictionary with a few duplicate values. This groups the dictionary key/value pairs by value. … Read more

C# – Get dictionary key by value

by

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

C# – Remove items from dictionary

by

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

C# – Get all files in a folder

by

There are two simple ways to get all files in a folder: I’ll show examples below, along with a few other scenarios, such as getting files from subfolders. Note: ‘directory’ and ‘folder’ mean the same thing. I use these terms interchangeably. Get all files with Directory.GetFiles() Directory.GetFiles() returns all file paths from the top-level folder … Read more

C# – Serialize to JSON in alphabetical order

by

There are two ways to serialize an object’s properties to JSON in alphabetical order using System.Text.Json: I’ll show how to do these two options below. Option 1 – Manually alphabetize with JsonPropertyOrder You can specify the exact serialization ordering by using the JsonPropertyOrder attribute. Therefore, to serialize in alphabetical order, first arrange the properties in … Read more

C# – Remove spaces from a string

by

The simplest way to remove spaces from a string is by using string.Replace(). Here’s an example: This outputs the following. Notice the spaces are removed. string.Replace() is good for removing all occurrences of a specific character (” ” in this case). When you want to remove all whitespace characters (spaces, tabs, newlines, etc..), there are … Read more

C# – Convert a List to a string

by

There are two good ways to convert a List<T> to a string: I’ll show examples of both approaches. Using String.Join() String.Join() is the simplest way to convert a List to a string. With this method, you pass in the List and a delimiter and it outputs a string. You can use any delimiter you want. … Read more

C# – Delete all files in a directory

by

Use Directory.EnumerateFiles() to get the file paths in a directory. Then loop over the file paths and delete each file. Here’s an example: This deletes the root directory’s files without deleting the directory itself. I’ll show more examples. Delete all files with a specific extension Use Directory.EnumerateFiles’ searchPattern pattern to search for files with a … Read more

C# – Read a text file line by line

by

There are two simple ways to read a text file line by line: Here’s an example of using File.ReadLines() to read a file line by line in a loop: This outputs the file’s lines: Here’s an example of using File.ReadAllLines() to read the same file into a string array and then loop through it. Skip … Read more

C# – How to use LinkedList

by

LinkedList<T> is a doubly linked list. It consists of nodes with values (i.e. integers, strings, etc…) and links to the next and previous node. LinkedList<T> has a reference to the head and tail nodes, which enables efficient insertion (and removal) from the start and end of the list. The main reason to use LinkedList<T> is … Read more

C# – Remove duplicates from a list

by

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

C# – Remove items from a list

by

Here are the different ways to remove items from a list: I’ll show examples of using these methods. Remove item by index with List.RemoveAt() You can use List.RemoveAt() to remove an item at an index (0-based). Here’s an example of removing the first and last item from the list: This removes the first item “A” … Read more

C# – Convert string list to int list

by

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

C# – How to sort a list

by

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

C# – Using a list of tuples

by

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

C# – How to sort a dictionary

by

Dictionaries are unordered data structures. Key/value pairs aren’t stored in sorted order. When you want the Dictionary in sorted order, there are two simple options: I’ll show both options. Sort Dictionary with OrderBy() Use OrderBy() (from System.Linq) to sort the Dictionary by key or value. It returns the Dictionary’s KeyValuePairs in ascending sorted order. I’ll … Read more

C# – Use SqlDbType.Structured for table parameters

by

To use a table-valued parameter (TVP) with SqlCommand (ADO.NET), pass in a DataTable as a SqlDbType.Structured parameter, like this: I’ll show a full example, starting with creating a TVP type and then inserting it as a SqlDbType.Structured parameter as shown above. 1 – Create the TVP type in SQL Server To be able to pass … Read more

C# – Serialize and deserialize a multidimensional array to JSON

by

System.Text.Json doesn’t support serializing / deserializing multidimensional arrays. When you try, it throws an exception like this – System.NotSupportedException: The type ‘System.Int[,] is not supported. You have three options: In this article, I’ll show an example of how to create a custom JsonConverter that handles multidimensional arrays. In this example, I’ll specifically show how to … Read more

C# – How to parse XML with XElement (Linq)

by

Use the XElement class (from the Linq-to-Xml API) to parse XML and work with it in memory. You can use this to search for XML elements, attributes, and modify values. This is an alternative to using an XML (de)serializer (which requires you to define a class that matches the XML structure). I’ll show examples of … Read more

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

by

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

How to debug .NET source code in Visual Studio

by

When you’re using the Visual Studio debugger to step through your code, sometimes it’s useful to be able to step into the .NET source code. I had to do this recently to figure out why my ASP.NET Core code wasn’t behaving as expected. You can enable .NET source code debugging with the following steps: Now … Read more