Garbage collection fails to reclaim BitmapImage?

Question

I have an application(WPF) which creates BitmapImages in huge numbers(like 25000). Seems like framework uses some internal logic so after creation there are approx 300 mb of

Answer 1

I followed the answer given by AAAA. Orignal code causing memory filled up is:

if (overlay != null) overlay.Dispose();
overlay = new Bitmap(backDrop);
Graphics g = Graphics.FromImage(overlay);

Inserted AAAA's code block, C# add "using System.Threading;" and VB add "Imports System.Threading":

if (overlay != null) overlay.Dispose();
//--------------------------------------------- code given by AAAA
Thread t = new Thread(new ThreadStart(delegate
{
    Thread.Sleep(500);
    GC.Collect();
}));
t.Start();
//-------------------------------------------- \code given by AAAA
overlay = new Bitmap(backDrop);
Graphics g = Graphics.FromImage(overlay);

Repeat looping this block now makes a steady and low memory footprint. This code worked using Visual Studio 2015 Community.