List<T>.CopyTo Method

Definition

Copies the List<T> or a portion of it to an array.

Overloads

CopyTo(T[], Int32)

Copies the entire List<T> to a compatible one-dimensional array, starting at the specified index of the target array.

CopyTo(Int32, T[], Int32, Int32)

Copies a range of elements from the List<T> to a compatible one-dimensional array, starting at the specified index of the target array.

CopyTo(T[])

Copies the entire List<T> to a compatible one-dimensional array, starting at the beginning of the target array.

Examples

The following example demonstrates all three overloads of the CopyTo method. A List<T> of strings is created and populated with 5 strings. An empty string array of 15 elements is created, and the CopyTo(T[]) method overload is used to copy all the elements of the list to the array beginning at the first element of the array. The CopyTo(T[], Int32) method overload is used to copy all the elements of the list to the array beginning at array index 6 (leaving index 5 empty). Finally, the CopyTo(Int32, T[], Int32, Int32) method overload is used to copy 3 elements from the list, beginning with index 2, to the array beginning at array index 12 (leaving index 11 empty). The contents of the array are then displayed.

using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        List<string> dinosaurs = new List<string>();

        dinosaurs.Add("Tyrannosaurus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("Mamenchisaurus");
        dinosaurs.Add("Brachiosaurus");
        dinosaurs.Add("Compsognathus");

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        // Declare an array with 15 elements.
        string[] array = new string[15];

        dinosaurs.CopyTo(array);
        dinosaurs.CopyTo(array, 6);
        dinosaurs.CopyTo(2, array, 12, 3);

        Console.WriteLine("\nContents of the array:");
        foreach(string dinosaur in array)
        {
            Console.WriteLine(dinosaur);
        }
    }
}

/* This code example produces the following output:

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Brachiosaurus
Compsognathus

Contents of the array:
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Brachiosaurus
Compsognathus

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Brachiosaurus
Compsognathus

Mamenchisaurus
Brachiosaurus
Compsognathus
 */

CopyTo(T[], Int32)

Source:
List.cs
Source:
List.cs
Source:
List.cs

Copies the entire List<T> to a compatible one-dimensional array, starting at the specified index of the target array.

public void CopyTo (T[] array, int arrayIndex);

Parameters

array
T[]

The one-dimensional Array that is the destination of the elements copied from List<T>. The Array must have zero-based indexing.

arrayIndex
Int32

The zero-based index in array at which copying begins.

Implements

Exceptions

array is null.

arrayIndex is less than 0.

The number of elements in the source List<T> is greater than the available space from arrayIndex to the end of the destination array.

Remarks

This method uses Array.Copy to copy the elements.

The elements are copied to the Array in the same order in which the enumerator iterates through the List<T>.

This method is an O(n) operation, where n is Count.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1
UWP 10.0

CopyTo(Int32, T[], Int32, Int32)

Source:
List.cs
Source:
List.cs
Source:
List.cs

Copies a range of elements from the List<T> to a compatible one-dimensional array, starting at the specified index of the target array.

public void CopyTo (int index, T[] array, int arrayIndex, int count);

Parameters

index
Int32

The zero-based index in the source List<T> at which copying begins.

array
T[]

The one-dimensional Array that is the destination of the elements copied from List<T>. The Array must have zero-based indexing.

arrayIndex
Int32

The zero-based index in array at which copying begins.

count
Int32

The number of elements to copy.

Exceptions

array is null.

index is less than 0.

-or-

arrayIndex is less than 0.

-or-

count is less than 0.

index is equal to or greater than the Count of the source List<T>.

-or-

The number of elements from index to the end of the source List<T> is greater than the available space from arrayIndex to the end of the destination array.

Remarks

This method uses Array.Copy to copy the elements.

The elements are copied to the Array in the same order in which the enumerator iterates through the List<T>.

This method is an O(n) operation, where n is count.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1
UWP 10.0

CopyTo(T[])

Source:
List.cs
Source:
List.cs
Source:
List.cs

Copies the entire List<T> to a compatible one-dimensional array, starting at the beginning of the target array.

public void CopyTo (T[] array);

Parameters

array
T[]

The one-dimensional Array that is the destination of the elements copied from List<T>. The Array must have zero-based indexing.

Exceptions

array is null.

The number of elements in the source List<T> is greater than the number of elements that the destination array can contain.

Remarks

This method uses Array.Copy to copy the elements.

The elements are copied to the Array in the same order in which the enumerator iterates through the List<T>.

This method is an O(n) operation, where n is Count.

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1
UWP 10.0