how can i close mdi child form without closing MDIproject

[Gimpster]

Simply type:

Unload MDIChild

where MDIChild is the name of the child form. You can use that to completely unload the form, or if you just want to hide it, you can type:

MDIChild.Hide

Either one will work to simply remove it from the user's screen. However, unloading it will free up more memory.