ReadOnlyCollection<T>.CopyTo(T[], Int32) Method

Definition

Namespace:

System.Collections.ObjectModel

Assemblies:

netstandard.dll, System.Runtime.dll

Source:

ReadOnlyCollection.cs

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

C#

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

Parameters

array

T[]

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

index

Int32

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

Implements

CopyTo(T[], Int32)

Exceptions

ArgumentNullException

array is null.

ArgumentOutOfRangeException

index is less than zero.

ArgumentException

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

Examples

The following code example demonstrates several members of the ReadOnlyCollection<T> class. The code example creates a List<T> of strings and adds four dinosaur names to it. The code example then wraps the list in a ReadOnlyCollection<T>.

After demonstrating the Count, Contains, Item[], and IList.IndexOf members, the code example shows that the ReadOnlyCollection<T> is just a wrapper for the original List<T> by adding a new item to the List<T> and displaying the contents of the ReadOnlyCollection<T>.

Finally, the code example creates an array larger than the collection and uses the CopyTo method to insert the elements of the collection into the middle of the array.

C#

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

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

        dinosaurs.Add("Tyrannosaurus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("Deinonychus");
        dinosaurs.Add("Compsognathus");

        ReadOnlyCollection<string> readOnlyDinosaurs =
            new ReadOnlyCollection<string>(dinosaurs);

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

        Console.WriteLine("\nCount: {0}", readOnlyDinosaurs.Count);

        Console.WriteLine("\nContains(\"Deinonychus\"): {0}",
            readOnlyDinosaurs.Contains("Deinonychus"));

        Console.WriteLine("\nreadOnlyDinosaurs[3]: {0}",
            readOnlyDinosaurs[3]);

        Console.WriteLine("\nIndexOf(\"Compsognathus\"): {0}",
            readOnlyDinosaurs.IndexOf("Compsognathus"));

        Console.WriteLine("\nInsert into the wrapped List:");
        Console.WriteLine("Insert(2, \"Oviraptor\")");
        dinosaurs.Insert(2, "Oviraptor");

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

        string[] dinoArray = new string[readOnlyDinosaurs.Count + 2];
        readOnlyDinosaurs.CopyTo(dinoArray, 1);

        Console.WriteLine("\nCopied array has {0} elements:",
            dinoArray.Length);
        foreach( string dinosaur in dinoArray )
        {
            Console.WriteLine("\"{0}\"", dinosaur);
        }
    }
}

/* This code example produces the following output:

Tyrannosaurus
Amargasaurus
Deinonychus
Compsognathus

Count: 4

Contains("Deinonychus"): True

readOnlyDinosaurs[3]: Compsognathus

IndexOf("Compsognathus"): 3

Insert into the wrapped List:
Insert(2, "Oviraptor")

Tyrannosaurus
Amargasaurus
Oviraptor
Deinonychus
Compsognathus

Copied array has 7 elements:
""
"Tyrannosaurus"
"Amargasaurus"
"Oviraptor"
"Deinonychus"
"Compsognathus"
""
 */

Remarks

This method uses Array.Copy to copy the elements.

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

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

Applies to