表单关闭时的可用内存

I have two forms "Main" and "Clients". Application starts with Main and it contains a button that opens the second one. But when I close Clients, Process Memory (Visual Studio diagnostic tools) don't reduce and if I open the form again it raises (like it creates another instance without destroying previous one). I've created the destructor method just to see if it's called but it didn't.I have two forms "Main" and "Clients". Applicat