C# WinForms highlight treenode when treeview doesnt have focus

What you are looking for is the HideSelection property on the TreeView.

From MSDN:

Gets or sets a value indicating whether the selected tree node remains highlighted even when the tree view has lost the focus.

Link: http://msdn.microsoft.com/en-us/library/system.windows.forms.treeview.hideselection.aspx

Code:

TreeView.HideSelection = false;

It is still shown but only in light grey which depending on your screen and current setup can be near in visible!

Override the OnDrawNode event. So you create and new class (call it "SpecialTreeView") an inherit from the Microsoft TreeView like class SpecialTreeView : TreeView. Then you add the following event override:

protected override void OnDrawNode(DrawTreeNodeEventArgs e)
{
    TreeNodeStates treeState = e.State;
    Font treeFont = e.Node.NodeFont ?? e.Node.TreeView.Font;

    // Colors.
    Color foreColor = e.Node.ForeColor;
    string strDeselectedColor = @"#6B6E77", strSelectedColor = @"#94C7FC";
    Color selectedColor = System.Drawing.ColorTranslator.FromHtml(strSelectedColor);
    Color deselectedColor = System.Drawing.ColorTranslator.FromHtml(strDeselectedColor);

    // New brush.
    SolidBrush selectedTreeBrush = new SolidBrush(selectedColor);
    SolidBrush deselectedTreeBrush = new SolidBrush(deselectedColor);

    // Set default font color.
    if (foreColor == Color.Empty)
        foreColor = e.Node.TreeView.ForeColor;

    // Draw bounding box and fill.
    if (e.Node == e.Node.TreeView.SelectedNode)
    {
        // Use appropriate brush depending on if the tree has focus.
        if (this.Focused)
        {
            foreColor = SystemColors.HighlightText;
            e.Graphics.FillRectangle(selectedTreeBrush, e.Bounds);
            ControlPaint.DrawFocusRectangle(e.Graphics, e.Bounds, foreColor, SystemColors.Highlight);
            TextRenderer.DrawText(e.Graphics, e.Node.Text, treeFont, e.Bounds,
                                         foreColor, TextFormatFlags.GlyphOverhangPadding);
        }
        else
        {
            foreColor = SystemColors.HighlightText;
            e.Graphics.FillRectangle(deselectedTreeBrush, e.Bounds);
            ControlPaint.DrawFocusRectangle(e.Graphics, e.Bounds, foreColor, SystemColors.Highlight);
            TextRenderer.DrawText(e.Graphics, e.Node.Text, treeFont, e.Bounds,
                                         foreColor, TextFormatFlags.GlyphOverhangPadding);
        }
    }
    else
    {
        if ((e.State & TreeNodeStates.Hot) == TreeNodeStates.Hot)
        {
            e.Graphics.FillRectangle(SystemBrushes.Window, e.Bounds);
            TextRenderer.DrawText(e.Graphics, e.Node.Text, hotFont, e.Bounds,
                                         System.Drawing.Color.Black, TextFormatFlags.GlyphOverhangPadding);
        }
        else
        {
            e.Graphics.FillRectangle(SystemBrushes.Window, e.Bounds);
            TextRenderer.DrawText(e.Graphics, e.Node.Text, treeFont, e.Bounds,
                                         foreColor, TextFormatFlags.GlyphOverhangPadding);
        }
    }
}

Compile the code and you should see "SpecialTreeView" in your tool box in the designer. Replace your TreeView with this new one using the same name and the only thing that will be different is the selection colours. When selected it will be selectedColor, when not selected the deselectedColor.

I hope this helps.

Fast solution:

Set the properties:

• HideSelection = false;
• DrawMode = TreeViewDrawMode.OwnerDrawText;

Then in the DrawNode event handler simply do:

private void treeView1_DrawNode(object sender, DrawTreeNodeEventArgs e) {
  e.DrawDefault = true;
}

On Windwos 7 this restores the old rendering, including the dashed box around the selection (which actually looks a bit outdated). The text will be white with focus, and black without focus. The background stays blue and visible.

This answer is not new, the others also contain these steps, but this is the minimal needed (at least in Windows 7, didn't test other OS's).