c#: size comparison of two strings (without using c#/java internal comparison function), sort in ascending order

Topic: First of all, you need to implement a function: a custom function for comparing the size of two strings (c#/java system functions are not allowed); then sort a string data in ascending order (when using string size comparison during the sorting process, using a custom string size comparison function).

Here's what I've come up with personally:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Demo
{
    class Program
    {
        /**
         * Compare the size of two strings (without using the internal comparison function of c#/java), sort in ascending order
         */
        static void Main(string[] args)
        {
            string[] strArr = new string[] { "a", "a2", "bc", "a1" };

            for (int i = 0; i < strArr.Length - 1; i++)
            {
                for (int j = i + 1; j < strArr.Length; j++)
                {
                    string temp = "";
                    if (Compare(strArr[i], strArr[j]) < 0)
                    {
                        temp = strArr[i];
                        strArr[i] = strArr[j];
                        strArr[j] = temp;
                    }
                }
            }

            foreach (string str in strArr)
            {
                Console.WriteLine(str);
            }

            Console.ReadKey();
        }

        static int Compare(string a, string b)
        {
            // If a=b=null, return a is equal to b 
            if (a == null && b == null )
                 return  0 ;

            // If a!=null and b=null, return a is greater than b 
            if (a != null && b == null )
                 return  1 ;

            // If a==null and b!=null, return a is less than b 
            if (a == null && b != null )
                 return - 1 ;

            char [] aArray = a.ToCharArray ();
            char [] bArray = b.ToCharArray ();

            // otherwise compare them directly 
            for ( int i = 0 ; i < aArray.Length; i++ )
            {
                if (i > bArray.Length - 1)
                    return 1;

                if (aArray[i] > bArray[i])
                {
                    return 1;
                }
                else  if (aArray [i] < bArray [i])
                {
                    return -1;
                }
                // If equal, do not process. . . 
            }

            // 此时则a.length==b.length或者b.length>a.length
            return (a.Length == b.Length) ? 0 : -1;
        }
    }
}