private bool CreateDocument()
{
    // Create an instance of the Tree provider first
    TreeProvider tree = new TreeProvider(CMSContext.CurrentUser);

    // Get the parent node - the API Example folder
    TreeNode parentNode = tree.SelectSingleNode(CMSContext.CurrentSiteName, "/API-Example", "en-us");

    if (parentNode != null)
    {
        // Create a new instance of the Tree node
        TreeNode newNode = TreeNode.New("CMS.MenuItem", tree);

        // Set the document's properties
        newNode.DocumentName = "My new document";
        newNode.DocumentCulture = "en-us";

        // Insert the document into the content tree
        newNode.Insert(parentNode);

        return true;
    }

    return false;
}

private bool InsertUnsortedAttachment()
{
    // Create a new instance of the Tree provider
    TreeProvider tree = new TreeProvider(CMSContext.CurrentUser);

    // Get the document
    TreeNode node = tree.SelectSingleNode(CMSContext.CurrentSiteName, "/API-Example", "en-us");

    // Path to the file to be inserted. This example uses an explicitly defined file path. However, you can use an object of the HttpPostedFile type (uploaded via an upload control).
    string postedFile = Server.MapPath("Files/file.png");

    if (node != null)
    {
        // Insert the attachment
        return (DocumentHelper.AddUnsortedAttachment(node, Guid.NewGuid(), postedFile, tree, ImageHelper.AUTOSIZE, ImageHelper.AUTOSIZE, ImageHelper.AUTOSIZE) != null);
    }

    return false;
}