MainActivity.cs

using System;
using System.Threading.Tasks;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;

namespace App20
{
    [Activity(Label = "MemTest", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        int count = 1;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            // Get our button from the layout resource,
            // and attach an event to it
            Button button = FindViewById<Button>(Resource.Id.MyButton);

            button.Click += delegate {
                button.Text = string.Format("{0} clicks!", count++);
                subClass myInst = new subClass();
            };
        }
    }
}

public class subClass
{
    const int Size = 48000000;
    //	const int Size = 36000000;
    const int NumMono = 1;
    int[][] pixel = new int[NumMono][];
    static int cnt = 0;
    static long totalMemory = 0;

    public subClass()
    {
        for (int i = 0; i < NumMono; i++)
            pixel[i] = null;
        while (true)
        {
            pixel[cnt % NumMono] = new int[Size];
            totalMemory = System.GC.GetTotalMemory(false);
            Console.WriteLine("++totalMemory(" + cnt + "): " + totalMemory + "");

            pixel[cnt % NumMono] = null;
            System.GC.Collect();
            totalMemory = System.GC.GetTotalMemory(false);
            Console.WriteLine("--totalMemory(" + cnt + "): " + totalMemory + "");

            cnt++;
            Task.Delay(100).Wait();
        }
    }
}