test.cs

private void addBlockToTreeView(List<MergeBlock> blocks, TreeNode node)
{
    foreach (MergeBlock block in blocks)
    {
        TreeNode curNode;

        if (node == null)
            curNode = treeView1.Nodes.Add(block.Name);
        else
            curNode = node.Nodes.Add(block.Name);

        foreach (MergeField field in block.MergeFields)
        {
            curNode.Nodes.Add(field.Name);
        }

        if (block.MergeBlocks != null)
            addBlockToTreeView(block.MergeBlocks, curNode);
    }
}