The ```Queue<T>``` generic class in the ```System.Collections.Generic``` namespace provides the **```CopyTo()``` method**, which can be used to copy a queue to an existing array at a specified index in C#.

# Syntax
```
public void CopyTo (T[] array, int arrayIndex);
```
This method takes as input a one-dimensional array where the elements will be copied from ```Queue<T>```, and an index at which the copying begins.

This method throws an exception if:
- The input array is null.
- The input index is less than zero.
- The number of elements in `Queue<T>` is greater than the total number of spaces available in the destination array from the specified index to the end of the array.

# Things to note
- This method works on one-dimensional arrays.

- This operation does not change the state of the queue.

- The elements are ordered in the array in the same way as the order of the elements from the start of the queue to the end.

- This is an $O(n)$ operation, where n is the count of the elements in the queue.


# Code
In this example, we create a queue of strings to store month names, and add the names of four months to it: March, April, May and June. After we add the elements, we print all the elements present in the queue.

After this, we create a new array of ```queueCopy``` strings with a size of ten elements that has two elements in it: January and February.
We now copy all the queue elements to this array with the ```CopyTo()``` method, starting from index two.

```months.CopyTo(queueCopy,2);```

We then print the elements of the array, and the array contains the queue elements in the same order from the specified index.

using System;
using System.Collections.Generic;

class QueueConverter
{
    static void Main()
    {
        Queue<string> months = new Queue<string>();
        months.Enqueue("March");
        months.Enqueue("April");
        months.Enqueue("May");
        months.Enqueue("June");

        Console.WriteLine("Queue Items : {0}", string.Join(",", months.ToArray()));
        string[] queueCopy = new string[10];
        queueCopy[0] = "January";
        queueCopy[1] = "February";
        Console.WriteLine("Array Items before Copy : {0}", string.Join(",", queueCopy));
        months.CopyTo(queueCopy,2);
        Console.WriteLine("Array Items after Copy : {0}", string.Join(",", queueCopy));


    }
}

How to copy a queue to an existing array in C#

The Queue generic class in the System.Collections.Generic namespace provides the CopyTo() method, which can be used to copy a queue to an existing array at a specified index in C#. Syntax public void CopyTo (T[] array, int arrayIndex);  This method takes as input a one-dimensional array where the elements will be copied from Queue, and an index at which the copying begins. This method throws an exception if:  The input array is null. The input index is less than zero. The number of elements in Queue is greater than the total number of spaces available in the destination array from the specified index to the end of the array.  Things to note   This method works on one-dimensional arrays.   This operation does not change the state of the queue.   The elements are ordered in the array in the same way as the order of the elements from the start of the queue to the end.   This is an O(n)O(n)O(n) operation, where n is the count of the elements in the queue.   