Quick Sort of Basic Algorithms

In the field of games, the algorithm is also a part, so I started to learn the algorithm,

Write a quick sort in C#

unity

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ValueAnd : MonoBehaviour {

    // Use this for initialization

    void Start()
    {
        int[] arr = { 1, 2, 3 ,4, 5, 6, 7,8};
        bubble(arr);
        foreach (var i in arr)
       {
            Debug.Log(i);
        }
	}

    void changeOther(int[] arr, int a, int b) //it’s nice
    {
        arr[a] = arr[a] + arr[b]; //sum
        arr[b] = arr[a] - arr[b]; //sum-b gets a
        arr[a] = arr[a] - arr[b]; //similarly get b
    }


    void bubble(int[] arr)
    {
        int lenth = arr.Length;
        for (int outSet = lenth - 1; outSet >= 1; outSet--)
        {
            bool First = true;
            for (int inner = 0; inner < lenth - 1; inner++)
            {
                Debug.Log(inner);
                if (arr[inner] > arr[inner + 1])
                {
                    changeOther(arr, arr[inner], arr[inner + 1]);

                    if (First)
                        First = false;
                }
            }
            Debug.Log(outSet);
            if (First){
                break;
                 }
        }
            
     }
｝

Two exchange methods, one is int a temp, and then exchange,

int a; int b; int temp;

temp=a;a=b;b=temp;

Well enough,

temp=a+b;

b=temp-b; 

a=temp-b;

First is whether the mark is the first time