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C# code examples · runnable

20 runnable C# code examples.

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C#

How to loop through an enum in C#Loop through every value of an enum in C# with Enum.GetValues<T>(), get the names with GetNames, turn an enum into a List, and handle the surprises: sort order, duplicate values, [Flags] members, generic helpers and display text.How to convert an int to an enum in C#Convert an int to an enum in C# with a cast, check the value with Enum.IsDefined first, get the int back with (int), get a member name from a value with ToString or Enum.GetName, and combine values with a [Flags] enum.How to check if a string contains a substring in C#Check if a C# string contains a substring with Contains, and do it case-insensitively with StringComparison.OrdinalIgnoreCase. Plus Ordinal vs InvariantCulture vs CurrentCulture, the Turkish-I trap, IndexOf, StartsWith and EndsWith, matching any of several words with SearchValues, and whole-word checks with Regex.How to iterate over a dictionary in C#Iterate over a C# Dictionary with foreach over KeyValuePair (or deconstructed into key and value), Keys and Values, why Keys + dict[key] does extra lookups, updating values, removing entries during the loop, iteration order, and merging two dictionaries.How to deep clone an object in C#Deep clone an object in C# with a hand-written DeepClone method or a System.Text.Json round trip, see why MemberwiseClone, record with and new List<T>(list) only copy one level, clone a generic list, and keep shared references and cycles intact.How to catch multiple exceptions in C#Catch multiple exceptions at once in C# with an exception filter, catch (Exception e) when (e is FormatException or OverflowException), order separate catch blocks correctly, filter on exception data, and rethrow properly: throw vs throw ex, wrapping with an inner exception, and ExceptionDispatchInfo.How to generate a random number in a range in C#Generate a random int between min and max in C# with Random.Shared.Next(min, max + 1), avoid the exclusive-bound off-by-one, fix the "Random keeps returning the same number" bug, get doubles and longs, shuffle a List<T>, and build random alphanumeric strings and secure tokens with RandomNumberGenerator.How to calculate the difference between two dates in C#Calculate the difference between two dates in C#: subtract DateTimes to get a TimeSpan, read Days vs TotalDays, count calendar days with DateOnly.DayNumber, calculate age from a birthday, split a gap into years, months and days, print relative time like "3 hours ago", and get the real elapsed time across DST with DateTimeOffset.How to check for null in C#Check for null in C# with is null and is not null, supply defaults with ?? and ??=, reach through possibly-null objects with ?. and ?[], work with int? and convert it to int, and track down and prevent NullReferenceException.How to sort a list of objects by property in C#Sort a C# List<T> of objects by a property with LINQ OrderBy(p => p.Name) or in place with list.Sort((a, b) => a.Age.CompareTo(b.Age)): descending order, ThenBy for ties, ordinal and case-insensitive strings, null keys, IComparable<T>, and sorting by a property name given as a string.How to convert a byte array to a hex string in C#Convert a byte array to a hex string in C# with Convert.ToHexString, get lowercase with ToHexStringLower, read hex back with Convert.FromHexString, know what BitConverter.ToString and the "x2" loop are still good for, and turn an int into hex and back with ToString("X") and NumberStyles.HexNumber.How to convert a string to a byte array in C#Convert a string to a byte array in C# with Encoding.UTF8.GetBytes and back with GetString, pick the right encoding, get the raw UTF-16 bytes without one, deal with the UTF-8 BOM, and decode invalid or chunked bytes safely.How to convert a string to an enum in C#Convert a string to an enum in C# with Enum.TryParse or Enum.Parse<T>, ignore case, reject numbers and comma lists that parse anyway, map your own codes and labels to enum values, and turn an enum back into a string with ToString(), nameof and format strings.How to remove duplicates from a list in C#Remove duplicates from a List<T> in C# with Distinct().ToList(), dedupe objects by a property with DistinctBy, remove duplicates in place with a HashSet, make Distinct() work on your own classes with records or Equals and GetHashCode, use Distinct with a lambda via EqualityComparer<T>.Create, and find or keep the last duplicate.How to loop with an index in C#Get the index of the current foreach iteration in C#: Index() on .NET 9+, the Select((item, i) => …) overload on older versions, a plain for loop for arrays and lists, a manual counter (and the continue and IndexOf traps), and Zip for walking two collections by position.How to group by with LINQ in C#Group items with LINQ in C#: GroupBy with a key selector, element and result selectors, grouping by multiple columns with anonymous types, tuples or records, query syntax (group … by … into), per-group Count/Sum and a HAVING filter, CountBy and AggregateBy, and ToLookup.How to convert an object to JSON in C#Convert an object to a JSON string in C# with System.Text.Json: JsonSerializer.Serialize, pretty printing and camelCase, renaming and hiding properties, enums as strings, leaving out null properties, fixing the "possible object cycle" error, and the \u escapes it writes for non-ASCII text.How to parse JSON into an object in C#Parse JSON into a C# object with System.Text.Json: JsonSerializer.Deserialize<T> into a record or class, case-insensitive and snake_case name matching, arrays, nested objects and dictionaries, JsonNode when you want a dynamic object, JsonDocument for read-only access, and strict parsing with required members and JsonException.How to convert a string to an int in C#Convert a string to an int in C# with int.TryParse for input you don't trust and int.Parse for text you do, see how Convert.ToInt32 differs, check whether a string is a number, parse hex, thousands separators and other formats, and move to long or BigInteger when the value is too big.How to join a list into a string in C#Join a C# List<string> or any IEnumerable<string> into one string with string.Join(", ", list), join numbers and objects with string.Join<T> and LINQ Select, handle null elements, concatenate with string.Concat instead of Aggregate, build strings with StringBuilder.AppendJoin without a trailing comma, and repeat a string.

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