treeView.ImageKey = "Value";
Debug.WriteLine(treeView.ImageIndex);
treeView.ImageKey = null;
Debug.WriteLine(treeView.ImageIndex);
treeView.ImageIndex = -1;
Debug.WriteLine(treeView.ImageIndex);

-1
0
0

TreeNode node1 = new TreeNode(string.Empty, 12, 12); // imageList1.Count = 5

if (e.Node.ImageIndex >= e.Node.TreeView.ImageList.Images.Count) // if there is no image
{
    int imagewidths = e.Node.TreeView.ImageList.ImageSize.Width;
    int textheight = TextRenderer.MeasureText(e.Node.Text, e.Node.NodeFont).Height;
    int x = e.Node.Bounds.Left - 3 - imagewidths / 2;
    int y = (e.Bounds.Top + e.Bounds.Bottom) / 2+1;

    Point point = new Point(x - imagewidths/2, y - textheight/2); // the new location for the text to be drawn

    TextRenderer.DrawText(e.Graphics, e.Node.Text, e.Node.NodeFont, point, e.Node.ForeColor);
}
else // drawn at the default location
    TextRenderer.DrawText(e.Graphics, e.Node.Text, e.Node.TreeView.Font, e.Bounds, e.Node.ForeColor);