Converting from IEnumerable to List in C#

Converting from IEnumerable to List in C#

To convert an IEnumerable to a List in C#, you can use the ToList extension method provided by LINQ. This method is defined on the IEnumerable<T> interface and returns a new List<T> instance that contains the elements of the original IEnumerable<T>.

Here's an example of how to use the ToList method to convert an IEnumerable<T> to a List<T>:

 IEnumerable<int> numbers = new[] { 1, 2, 3, 4, 5 }; List<int> numberList = numbers.ToList();

In this example, we first create an IEnumerable<int> called numbers that contains five integer values. We then call the ToList method on the numbers object, which returns a new List<int> that contains the same elements as the numbers object.

Note that the ToList method is an extension method defined in the System.Linq namespace, so you will need to add a using directive for this namespace at the top of your C# file in order to use this method.

Examples

1. "Convert IEnumerable to List using ToList() method"

Code:

IEnumerable<int> numbers = GetNumbers(); List<int> listNumbers = numbers.ToList();

Description:

Uses the ToList() extension method to convert an IEnumerable to a List.

2. "Convert IEnumerable to List with custom type"

Code:

IEnumerable<Person> people = GetPeople(); List<Person> personList = people.ToList();

Description:

Applies the ToList() method to convert an IEnumerable of custom objects to a List.

3. "Convert IEnumerable to List with filtering"

Code:

IEnumerable<int> allNumbers = GetAllNumbers(); List<int> filteredNumbers = allNumbers.Where(n => n > 5).ToList();

Description:

Combines LINQ's Where method with ToList() to filter and convert an IEnumerable to a List.

4. "Convert IEnumerable to List with projection"

Code:

IEnumerable<string> words = GetWords(); List<int> wordLengths = words.Select(w => w.Length).ToList();

Description:

Utilizes the Select method to project each element and then applies ToList() for conversion.

5. "Convert IEnumerable to List using List constructor"

Code:

IEnumerable<char> characters = GetCharacters(); List<char> charList = new List<char>(characters);

Description:

Constructs a new List using the List constructor that takes an IEnumerable.

6. "Convert IEnumerable to List with distinct values"

Code:

IEnumerable<int> duplicateNumbers = GetDuplicateNumbers(); List<int> uniqueNumbers = duplicateNumbers.Distinct().ToList();

Description:

Uses Distinct() method to remove duplicates before converting to a List.

7. "Convert IEnumerable to List with specified capacity"

Code:

IEnumerable<string> words = GetWords(); List<string> wordList = new List<string>(words.Count()); wordList.AddRange(words);

Description:

Initializes a List with a specified capacity and then adds elements from the IEnumerable.

8. "Convert IEnumerable to List with custom comparer"

Code:

IEnumerable<string> words = GetWords(); List<string> caseInsensitiveList = words.ToList(StringComparer.OrdinalIgnoreCase);

Description:

Uses an overload of ToList that allows specifying a custom comparer (case-insensitive in this example).

9. "Convert IEnumerable to List with condition"

Code:

IEnumerable<int> numbers = GetNumbers(); List<int> evenNumbers = numbers.Where(n => n % 2 == 0).ToList();

Description:

Applies a condition using Where before converting to a List.

10. "Convert IEnumerable to List with sorting"

Code:

IEnumerable<string> unsortedWords = GetUnsortedWords(); List<string> sortedWords = unsortedWords.OrderBy(w => w).ToList();

Description:

Sorts the elements using OrderBy before converting the IEnumerable to a List.

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