C# | Copy OrderedDictionary elements to Array instance at the specified index

OrderedDictionary.CopyTo(Array, Int32) method is used to copy the OrderedDictionary elements to a one-dimensional Array object at the specified index.

Syntax:

public void CopyTo (Array array, int index);

Parameters:

array: It is the one-dimensional Array which is the destination of the DictionaryEntry objects copied from OrderedDictionary. The Array must have zero-based indexing.

index: it is the zero-based index in array at which copying begins.

Note: OrderedDictionary.CopyTo(Array, Int32) method doesn’t provide any guarantee to maintain the order of the elements in the OrderedDictionary collection.

Below programs illustrate the use of the above-discussed method:

Example 1:

// C# code to copy OrderedDictionary to
// Array instance at the specified index
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a orderedDictionary named myDict
        OrderedDictionary myDict = new OrderedDictionary();

        // Adding key and value in myDict
        myDict.Add("key1", "value1");
        myDict.Add("key2", "value2");
        myDict.Add("key3", "value3");
        myDict.Add("key4", "value4");
        myDict.Add("key5", "value5");

        DictionaryEntry[] myArr = new DictionaryEntry[myDict.Count];

        // Copying OrderedDictionary to Array
        // instance at the specified index
        myDict.CopyTo(myArr, 0);

        // Displaying elements in myArr
        for (int i = 0; i < myArr.Length; i++) {
            Console.WriteLine(myArr[i].Key + "-->"
                                + myArr[i].Value);
        }
    }
}

Output:

key3-->value3
key4-->value4
key5-->value5
key2-->value2
key1-->value1

Example 2:

// C# code to copy OrderedDictionary to
// Array instance at the specified index
// that give ArgumentOutOfRangeException
// due to the negative index
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a orderedDictionary named myDict
        OrderedDictionary myDict = new OrderedDictionary();

        // Adding key and value in myDict
        myDict.Add("C", "1");
        myDict.Add("C++", "2");
        myDict.Add("Java", "3");
        myDict.Add("C#", "4");

        DictionaryEntry[] myArr = new DictionaryEntry[myDict.Count];

        // Copying OrderedDictionary to Array
        // instance at the specified index
        // This will raise "ArgumentOutOfRangeException"
        // as index is less than 0
        myDict.CopyTo(myArr, -2);

        // Displaying elements in myArr
        for (int i = 0; i < myArr.Length; i++) {
            Console.WriteLine(myArr[i].Key + "-->"
                                + myArr[i].Value);
        }
    }
}

Runtime Error:

Unhandled Exception:
System.ArgumentOutOfRangeException: Non-negative number required.
Parameter name: arrayIndex

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.specialized.ordereddictionary.copyto?view=netframework-4.7.2