Directory & File browsing...

There are plenty of tutorials/articles/tidbits on how to use the TreeView and how to inspect the file system. Did you try Googling?

One small point you'll want to consider. Since you don't want to load up the entire file system structure at once, you'll probably only want to load one level in the tree at a time. When a node is expanded, you'd then load all the folders in that folder. I'm sure there is an event on the TreeView you can use to implement this (e.g., Expanded or something along those lines).

http://www.c-sharpcorner.com/UploadFile/nkumar/WindowsExplorerinCSharp11292005230454PM/WindowsExplorerinCSharp.aspx

Ever heard of google?

protected void AppendDirectoriesToTreeNode(TreeNode node, string root)
{
    DirectoryInfo rootDir = new DirectoryInfo(root);
    foreach (DirectoryInfo subDir in rootDir.GetDirectories())
    {
        TreeNode subdirNode = new TreeNode(subDir.Name);
        AppendDirectoriesToTreeNode(subdirNode, subDir.FullName);
        foreach (FileInfo fileInfo in subDir.GetFiles())
        {
            subdirNode.Nodes.Add(fileInfo.Name);
        }
        node.Nodes.Add(subdirNode);
    }
}

I googled this phrase:

"c# treeview folder hierarchy"

and got 334,000 results back.