C# | Copy StringDictionary to Array at the specified index

StringDictionary.CopyTo(Array, Int32) method is used to copy the string dictionary values to a one-dimensional Array instance at the specified index.

Syntax:

public virtual void CopyTo (Array array, int index);

Parameters:

• array: It is the one-dimensional Array which is the destination of the values copied from the StringDictionary.
• index: It is the index in the array where copying begins.

Exceptions:

• ArgumentNullException : If the key is null.
• ArgumentOutOfRangeException : If the index is less than the lower bound of array.
• ArgumentException : If the array is multidimensional Or the number of elements in the StringDictionary is greater than the available space from index to the end of array.

Below programs illustrate the use of StringDictionary.CopyTo(Array, Int32) method:

Example 1:

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

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a StringDictionary named myDict
        StringDictionary myDict = new StringDictionary();

        // Adding key and value into the StringDictionary
        myDict.Add("A", "Apple");
        myDict.Add("B", "Banana");
        myDict.Add("C", "Cat");
        myDict.Add("D", "Dog");
        myDict.Add("E", "Elephant");

        // Creating an Array named myArr
        DictionaryEntry[] myArr = { new DictionaryEntry(),
                                    new DictionaryEntry(),
                                    new DictionaryEntry(),
                                    new DictionaryEntry(),
                                    new DictionaryEntry() };

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

        // Displaying key and value pairs in Array myArr
        for (int i = 0; i < myArr.Length; i++) {
            Console.WriteLine(myArr[i].Key + " " + myArr[i].Value);
        }
    }
}

Output:

d Dog
b Banana
c Cat
e Elephant
a Apple

Example 2:

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

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a StringDictionary named myDict
        StringDictionary myDict = new StringDictionary();

        // Adding key and value into the StringDictionary
        myDict.Add("A", "Apple");
        myDict.Add("B", "Banana");
        myDict.Add("C", "Cat");
        myDict.Add("D", "Dog");
        myDict.Add("E", "Elephant");

        // Creating an Array named myArr
        DictionaryEntry[] myArr = { new DictionaryEntry(),
                                    new DictionaryEntry(),
                                    new DictionaryEntry() };

        // Copying StringDictionary to
        // Array at the specified index
        // This should raise "ArgumentException" as
        // the number of elements in the StringDictionary
        // is greater than the available space from
        // index to the end of array.
        myDict.CopyTo(myArr, 0);

        // Displaying key and value pairs in Array myArr
        for (int i = 0; i < myArr.Length; i++) {
            Console.WriteLine(myArr[i].Key + " " + myArr[i].Value);
        }
    }
}

Runtime Error:

Unhandled Exception:
System.ArgumentException: Destination array is not long enough to copy all the items in the collection. Check array index and length.

Note:

• The elements copied to the Array are sorted in the same order that the enumerator iterates through the StringDictionary.
• This method is an O(n) operation, where n is Count.

Reference:

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