C# - Swap Methods - Dot Net Perls

Swap. A Swap method exchanges array element values. It acts on 2 separate elements so that they both are still present but in opposite locations.

In the C# language, there is no built-in method for this purpose on most types. You have to implement a custom swap method for string characters and other types.

This example shows how to swap two characters in a string's character buffer. It also shows how to swap two elements in an array with elements of type Int32.

int

Info For SwapCharacters, we use the ToCharArray method and the new string constructor and return a new string reference.

String Constructor

String ToCharArray

Note The string type is immutable and you cannot assign characters to locations in a string directly.

Next For SwapInts, the code uses a temporary variable, but the int array is modified in-place so no reference must be returned.

int Array

using System;

class Program
{
    static void Main()
    {
        // Swap characters in the string.
        string value1 = "abc";
        string swap1 = SwapCharacters(value1, 0, 1);
        Console.WriteLine(swap1);

        // Swap elements in array.
        int[] array1 = { 1, 2, 3, 4, 5 };
        SwapInts(array1, 0, 1);
        foreach (int element in array1)
        {
            Console.Write(element);
        }
        Console.WriteLine();
    }

    static string SwapCharacters(string value, int position1, int position2)
    {
        // Swaps characters in a string.
        char[] array = value.ToCharArray();
        char temp = array[position1];
        array[position1] = array[position2];
        array[position2] = temp;
        return new string(array);
    }

    static void SwapInts(int[] array, int position1, int position2)
    {
        // Swaps elements in an array.
        int temp = array[position1];
        array[position1] = array[position2];
        array[position2] = temp;
    }
}
bac
21345

Exceptions. This code will cause exceptions if you call it with invalid parameters. If needed, you can validate the arguments with if-statements and then throw.

Note This negatively impacts performance in tight loops—it is only necessary when many callers will exist.

ArgumentException

IndexOutOfRangeException

It is possible to develop methods that swap characters in a string or elements in an array. These methods were tested and proven correct on the input provided.

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This page was last updated on May 11, 2023 (rewrite).

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