C# Convert List to Array

Use the ToArray and ToList methods to convert Lists and arrays.
Convert List, array. A List can be converted to an array. The opposite conversion is also possible. In each conversion, the element types remain the same—strings remain strings.Convert
More complex methods can be implemented. A for-loop can copy elements from a List and add them to an array. But this is more work for the programmer.
List to array. Here we convert a string List into a string array of the same number of elements. At the end, the program prints the array's length.

Step 1: We create a List and populate it with some strings. The List here can only hold strings (or null).


Step 2: Next we use ToArray on the List. To test it, we pass the string array to the Test() method.

C# program that converts List to array using System; using System.Collections.Generic; class Program { static void Main() { // Step 1: create list. List<string> list = new List<string>(); list.Add("one"); list.Add("two"); list.Add("three"); list.Add("four"); list.Add("five"); // Step 2: convert to string array. string[] array = list.ToArray(); Test(array); } static void Test(string[] array) { Console.WriteLine("Array received: " + array.Length); } } Output Array received: 5
Array to List. We can convert an array of any number of elements to a List that has the same type of elements. There are 3 parts to this example.

Part 1: Here we initialize a new string array containing 5 strings. These are specified as string literals.

Part 2: Here we convert the array to a List with the List constructor. This returns a new List of strings.

Part 3: Here the example converts the array to a List with the ToList() instance method.

C# program that uses List constructor and ToList using System; using System.Collections.Generic; using System.Linq; class Program { static void Main() { // Part 1: string array. string[] array = new string[] { "one", "two", "three", "four", "five" }; // Part 2: use list constructor. List<string> list1 = new List<string>(array); Test(list1); // Part 3: use ToList method. List<string> list2 = array.ToList(); Test(list2); } static void Test(List<string> list) { Console.WriteLine("List count: " + list.Count); } } Output List count: 5 List count: 5
Notes, extension method. The ToList method is an extension method from System.Linq. This kind of method is an addition to normal C# method calls.ToListExtension
Internals. You can use the IL Disassembler tool provided by Microsoft to look inside methods. The ToList method calls the List constructor.

So: That means parts 2 and 3 above are the same except for a check against the null literal.

IL Disassembler Tutorial
Implicit conversion error. You may get the "Cannot implicitly convert type" error. This error raised by the compiler tells you that the type needs a regular cast or is not compatible.

Note: If your code statement tries to assign a List to an array, you will get this error.

Readability. It is easy to remember that ToList converts a collection to a List, and ToArray does the same for an array. These methods are well-named.

Performance: I have not performed extensive micro-benchmarks on these conversion methods.

Note: The new List constructor would be the fastest for that example. A loop that copies elements would be similar.

A summary. Convert your arrays to Lists and vice versa with this code. You can't simply assign one to the other. The List constructor can also be used (and it avoids a null check).
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