In addition to solution posted by Maciej Los, you definitelly should look at
System.IO namespace which contain all informations about managing files and directories:
http://msdn.microsoft.com/en-us/library/system.io.aspx[
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You should distinct between manage data (such as create/rename/delete file or directory) and presenting that data on TreeView (or any other component). You are not creating/deleting files or directories via TreeView component. It's purpose is to present data only.
You can access all elements in TreeView control using TreeView.Nodes property. Then you can get what data is selected (file or directory) and do whatever you want with that information. If you have selected directory then you can add or delete child directories. It's all up to you.
Good start with using TreeView component is here:
http://www.dotnetperls.com/treeview[
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http://msdn.microsoft.com/en-us/library/system.windows.forms.treeview%28v=vs.110%29.aspx[
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Cheers!