Question

I have a treeview and a imageList which contain 1 icon (folder.ico), I want to set icon only for root node, child node will don’t have icon, so I try to set image index for child node but it have some problem, look the picture:

My code:

        ImageList imageList = new ImageList();
        imageList.Images.Add(Image.FromFile(System.AppDomain.CurrentDomain.BaseDirectory.Replace("\\bin\\Debug\\","") + "\\Images\\folder.ico"), Color.Transparent);
        treeView1.ImageList = imageList;
        foreach (TreeNode node in treeView1.Nodes)
        {
            foreach (TreeNode node2 in node.Nodes)
            {
                node2.ImageIndex = 100;
                node2.SelectedImageIndex = 100;
            }
        }

Thanks

EDIT
I create a Custom TreeView at the answer of @Killercam:

class CustomTreeView : TreeView
{
public const int NOIMAGE = -1;

public CustomTreeView()
    : base()
{
    // .NET Bug: Unless LineColor is set, Win32 treeview returns -1 (default), .NET returns Color.Black!
    base.LineColor = SystemColors.GrayText;
    base.DrawMode = TreeViewDrawMode.OwnerDrawAll;
}

protected override void OnDrawNode(DrawTreeNodeEventArgs e)
{
    // Space between Image and Label.
    const int SPACE_IL = 3;  

    // We only do additional drawing.
    e.DrawDefault = true;
    base.OnDrawNode(e);
    if (base.ShowLines && base.ImageList != null && e.Node.ImageIndex == NOIMAGE
        // exclude root nodes, if root lines are disabled
        //&& (base.ShowRootLines || e.Node.Level > 0))
            )
    {
        // Using lines & images, but this node has none: fill up missing treelines

        // Image size
        int imgW = base.ImageList.ImageSize.Width;
        int imgH = base.ImageList.ImageSize.Height;

        // Image center
        int xPos = e.Node.Bounds.Left - SPACE_IL - imgW / 2;
        int yPos = (e.Node.Bounds.Top + e.Node.Bounds.Bottom) / 2;

        // Image rect
        Rectangle imgRect = new Rectangle(xPos, yPos, 0, 0);
        imgRect.Inflate(imgW / 2, imgH / 2);

        using (Pen p = new Pen(base.LineColor, 1))
        {
            p.DashStyle = DashStyle.Dot;

            // Account uneven Indent for both lines.
            p.DashOffset = base.Indent % 2;

            // Horizontal treeline across width of image
            // account uneven half of delta ItemHeight & ImageHeight.
            int yHor = yPos + ((base.ItemHeight - imgRect.Height) / 2) % 2;

            //if (base.ShowRootLines || e.Node.Level > 0)
            //{
            //    e.Graphics.DrawLine(p, imgRect.Left, yHor, imgRect.Right, yHor);
            //}
            //else
            //{
            //    // for root nodes, if root lines are disabled, start at center
            //    e.Graphics.DrawLine(p, xPos - (int)p.DashOffset, yHor, imgRect.Right, yHor);
            //}

            e.Graphics.DrawLine(p,
                    (base.ShowRootLines || e.Node.Level > 0) ? imgRect.Left : xPos - (int)p.DashOffset,
                    yHor, imgRect.Right, yHor);
            if (!base.CheckBoxes && e.Node.IsExpanded)
            {
                // Vertical treeline , offspring from NodeImage center to e.Node.Bounds.Bottom
                // yStartPos: account uneven Indent and uneven half of delta ItemHeight & ImageHeight
                int yVer = yHor + (int)p.DashOffset;
                e.Graphics.DrawLine(p, xPos, yVer, xPos, e.Node.Bounds.Bottom);
            }
        }
    }
}

protected override void OnAfterCollapse(TreeViewEventArgs e)
{
    base.OnAfterCollapse(e);
    if (!base.CheckBoxes && base.ImageList != null && e.Node.ImageIndex == NOIMAGE)
    {
        // DrawNode event not raised: redraw node with collapsed treeline
        base.Invalidate(e.Node.Bounds);
    }
}
}

Then use it in my code:

private void TestCustomTreeView_Load(object sender, EventArgs e)
    {
        // @Killercam EDIT: Set the default Image to one that is not used.
        valForm.siteTreeView.ImageIndex = 100;
        valForm.siteTreeView.SelectedImageIndex = 100;

        TemplateCustomTreeView myTree = new TemplateCustomTreeView();
        myTree.Font = new System.Drawing.Font("Tahoma", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));

        myTree.Location = new System.Drawing.Point(6, 26);
        myTree.Name = "tree";
        myTree.Scrollable = true;
        myTree.Size = new System.Drawing.Size(320, 296);
        myTree.ImageList = imageList1;
        /*Add item*/
        TreeNode node = new TreeNode();
        node.Name = "abc1";
        node.Text = "abc1";
        node.ImageIndex = 0;
        myTree.Nodes.Add(node);
        TreeNode node3 = new TreeNode();
        node3.Name = "abc2";
        node3.Text = "abc2";
        node3.ImageIndex = -1;            
        node.Nodes.Add(node3);
        ////
        TreeNode node2 = new TreeNode();
        node2.Name = "abc3";
        node2.Text = "abc3";
        node2.ImageIndex = 0;
        myTree.Nodes.Add(node2);
        this.Controls.AddRange(new System.Windows.Forms.Control[] { myTree });

    }
}

The result still not work, It’s still have a folder icon before the text!

Answer 1

You can’t do what you require

"All I want is don't show icon at child node."

without overriding the control. I also have found that you cannot display different images for different nodes with the standard WinForms TreeView. Below is some code that will make the TreeView look better; that is will draw the small section of the tree line for the sub-nodes.

class CustomTreeView : TreeView
{
    public const int NOIMAGE = -1;

    public CustomTreeView()
        : base()
    {
        // .NET Bug: Unless LineColor is set, Win32 treeview returns -1 (default), .NET returns Color.Black!
        base.LineColor = SystemColors.GrayText;
        base.DrawMode = TreeViewDrawMode.OwnerDrawAll;
    }

    protected override void OnDrawNode(DrawTreeNodeEventArgs e)
    {
        // Space between Image and Label.
        const int SPACE_IL = 3;  

        // We only do additional drawing.
        e.DrawDefault = true;
        base.OnDrawNode(e);
        if (base.ShowLines && base.ImageList != null && e.Node.ImageIndex == NOIMAGE
            // exclude root nodes, if root lines are disabled
            //&& (base.ShowRootLines || e.Node.Level > 0))
                )
        {
            // Using lines & images, but this node has none: fill up missing treelines

            // Image size
            int imgW = base.ImageList.ImageSize.Width;
            int imgH = base.ImageList.ImageSize.Height;

            // Image center
            int xPos = e.Node.Bounds.Left - SPACE_IL - imgW / 2;
            int yPos = (e.Node.Bounds.Top + e.Node.Bounds.Bottom) / 2;

            // Image rect
            Rectangle imgRect = new Rectangle(xPos, yPos, 0, 0);
            imgRect.Inflate(imgW / 2, imgH / 2);

            using (Pen p = new Pen(base.LineColor, 1))
            {
                p.DashStyle = DashStyle.Dot;

                // Account uneven Indent for both lines.
                p.DashOffset = base.Indent % 2;

                // Horizontal treeline across width of image
                // account uneven half of delta ItemHeight & ImageHeight.
                int yHor = yPos + ((base.ItemHeight - imgRect.Height) / 2) % 2;

                //if (base.ShowRootLines || e.Node.Level > 0)
                //{
                //    e.Graphics.DrawLine(p, imgRect.Left, yHor, imgRect.Right, yHor);
                //}
                //else
                //{
                //    // for root nodes, if root lines are disabled, start at center
                //    e.Graphics.DrawLine(p, xPos - (int)p.DashOffset, yHor, imgRect.Right, yHor);
                //}

                e.Graphics.DrawLine(p,
                        (base.ShowRootLines || e.Node.Level > 0) ? imgRect.Left : xPos - (int)p.DashOffset,
                        yHor, imgRect.Right, yHor);
                if (!base.CheckBoxes && e.Node.IsExpanded)
                {
                    // Vertical treeline , offspring from NodeImage center to e.Node.Bounds.Bottom
                    // yStartPos: account uneven Indent and uneven half of delta ItemHeight & ImageHeight
                    int yVer = yHor + (int)p.DashOffset;
                    e.Graphics.DrawLine(p, xPos, yVer, xPos, e.Node.Bounds.Bottom);
                }
            }
        }
    }

    protected override void OnAfterCollapse(TreeViewEventArgs e)
    {
        base.OnAfterCollapse(e);
        if (!base.CheckBoxes && base.ImageList != null && e.Node.ImageIndex == NOIMAGE)
        {
            // DrawNode event not raised: redraw node with collapsed treeline
            base.Invalidate(e.Node.Bounds);
        }
    }
}

This will give you a TreeView that looks like:

Here my master node (Node[0]) is the one without a specified Image and is what you require for your File1/File2 nodes.

I hope this helps.