Create project folder Buildengine

When I am creating one project file by code using the BuidEngine, Does anybody know..

1. how to add project folders?
2. how to add one builditem to the crea开发者_StackOverflow社区ted folder?

.

var project = new Project();
project.Load(ProjectFile.FullName, ProjectLoadSettings.IgnoreMissingImports);
//Create project folder
var buildItem = project.AddNewItem(itemName, fileName);
//add file to folder

Thanks in advance

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What do you mean by project folder? Won't specifying filename like Folder\File1 do the trick?