Memory is not released after dispose method is calling in wpf prism

Question

I have navigating from one window to another modal window. There are 10 observable collection. After closing the window, i have set null to the all observable collection. But in task manager the memory is not reduced. When I open the modal window 25 mb is increased but when i close the window only 1mb or 2mb only reduced after disposing all observable collection.

private bool disposedValue = false;
protected virtual void Dispose(bool disposing)
{
   if (!disposedValue)
   {
       if (disposing)
       {
           Collection1 = null;
           Collection2 = null;
           Collection3 = null;
           Collection4 = null;
           Collection5 = null;
       }
       disposedValue = true;
   }
}

Please suggestion me i have did anything wrong. Please share your valuable suggestion. I have also checked the memory consumption in visual studio Diagnostic Tools.

Answer 1

Not sure about the negative side , but work for sure

public class MemoryManagement
    {
        /// <summary>
        /// Clear un wanted memory
        /// </summary>
        public static void FlushMemory()
        {
            try
            {
                GC.Collect();
                GC.WaitForPendingFinalizers();
                if (Environment.OSVersion.Platform == PlatformID.Win32NT)
                {
                    SetProcessWorkingSetSize(System.Diagnostics.Process.GetCurrentProcess().Handle, -1, -1);
                }
            }
            catch (Exception e)
            {
            }
        }

        /// <summary>
        /// set process working size
        /// </summary>
        /// <param name="process">Gets process</param>
        /// <param name="minimumWorkingSetSize">Gets minimum working size</param>
        /// <param name="maximumWorkingSetSize">Gets maximum working size</param>
        /// <returns>Returns value</returns>
        [DllImportAttribute("kernel32.dll", EntryPoint = "SetProcessWorkingSetSize", ExactSpelling = true, CharSet =
          CharSet.Ansi, SetLastError = true)]
        private static extern int SetProcessWorkingSetSize(IntPtr process, int minimumWorkingSetSize, int maximumWorkingSetSize);
    }

Call MemoryManagement.FlushMemory() in the Dispose