实现方式一：
通过代码方式实现如下所示：
private string FilePath = Application.StartupPath + "\Images\";
Image img = new Bitmap(FilePath + "one.ico");
Image img1 = new Bitmap(FilePath + "two.ico");
ImageList imgs = new ImageList();
imgs.Images.Add(img);
imgs.Images.Add(img1);
this.tvTest.ImageList = imgs;
TreeNode node = new TreeNode();
node.Text = "Root";
this.tvTest.Nodes.Add(node);
node.ImageIndex = 0;
node.SelectedImageIndex = 0;
TreeNode node1 = new TreeNode();
node1.Text = "root001";
TreeNode node2 = new TreeNode();
node2.Text = "root002";
node.Nodes.Add(node1);
node.Nodes.Add(node2);
this.tvTest.ExpandAll();
node1.ImageIndex =1;
node1.SelectedImageIndex = 1;
node2.ImageIndex = 1;
node2.SelectedImageIndex = 1;
实现方式二：
通过绑定ImageList控件实现，如下所示：
操作步骤：第一步，工具箱中拖动ImageList控件；第二步，ImageList控件Images属性添加图片集合；第三步，TreeView控件绑定ImageList属性；
第四步，代码如下所示：
TreeNode node = new TreeNode();
node.Text = "Root";
this.tvTest.Nodes.Add(node);
node.ImageIndex = 0;
node.SelectedImageIndex = 0;
TreeNode node1 = new TreeNode();
node1.Text = "root001";
TreeNode node2 = new TreeNode();
node2.Text = "root002";
node.Nodes.Add(node1);
node.Nodes.Add(node2);
this.tvTest.ExpandAll();
node1.ImageIndex =1;
node1.SelectedImageIndex = 1;
node2.ImageIndex = 1;
node2.SelectedImageIndex = 1;
运行效果如下：
