Hi Dieter,

I performed a test based on your description and did reproduce the problem
on my side.

This problem is caused by the Vista visual styles. If you disable the
visual styles for the application, the problem doesn't exist.

FYI, to disable the visual styles for a WinForm application, if you're
using C#, open the Program.cs file and comment out the line of code
'Application.EnableVisualStyles();' in the static Main method; if you're
using VB.NET, right click the project in the Solution Explorer and choose
Properties, in the Project Designer, switch to Application tab and clear
the checkbox before the option 'Enable XP visual styles'.

So, the easiest workaround of this problem is to disable the Vista visual
styles for the application.

A more complicated workaround is to draw the TreeView by ourselves so that
we can ensure the displayed check state of the treenode is always correct.
To do this, we need to set the DrawMode of the TreeView to OwnerDrawAll and
handle the DrawNode event of the TreeView. In addition, we need to add two
bmp files to the application. One bmp file represents the plus sign used by
the TreeView and the other represents the minus sign.

The following is a sample to do this:

public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
           this.treeView1.DrawMode = TreeViewDrawMode.OwnerDrawAll;
           this.treeView1.DrawNode += new
DrawTreeNodeEventHandler(treeView1_DrawNode);
       }

       void treeView1_DrawNode(object sender, DrawTreeNodeEventArgs e)
       {            
           int left = e.Bounds.X;
           int top = e.Bounds.Y;
           int height = e.Bounds.Height;

           int nodeleft = e.Node.Bounds.X;
           int nodetop = e.Node.Bounds.Y;
           int nodeheight = e.Node.Bounds.Height;
           int nodewidth = e.Node.Bounds.Width;

           int linelength =10;
           int checkboxwidth = 13;
           int checknodespace = 2;
           using (Pen p = new Pen(Color.Gray))
           {
               p.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot;
               int lineleft =
nodeleft-checknodespace-checkboxwidth-linelength;
               //draw horizontal dot line
               e.Graphics.DrawLine(p, lineleft, top + height / 2, lineleft
+ linelength, top + height / 2);
               // draw the up half vertical dot line
               if (e.Node.PrevNode != null || e.Node.Parent != null)
               {
                   e.Graphics.DrawLine(p, lineleft, top, lineleft, top +
height / 2);
               }
               // draw the down half vertical dot line
               if (e.Node.NextNode != null)
               {
                   e.Graphics.DrawLine(p, lineleft, top + height / 2,
lineleft, e.Node.NextNode.Bounds.Top);
               }
               // draw plus/minus image
               if (e.Node.Nodes.Count > 0)
               {
                   if (!e.Node.IsExpanded)
                   {
                       e.Graphics.DrawImage(Properties.Resources.plus,
lineleft - Properties.Resources.plus.Width / 2, top + (height -
Properties.Resources.plus.Height) / 2);
                   }
                   else
                   {
                       e.Graphics.DrawImage(Properties.Resources.minus,
lineleft - Properties.Resources.minus.Width / 2, top + (height -
Properties.Resources.minus.Height) / 2);
                   }                            
               }
               // draw the vertical dot line for the parent nodes if
necessary
               TreeNode parentNode = e.Node.Parent;
               int parentNodeLeftDistance = checknodespace + checkboxwidth
+ linelength;
               while (parentNode != null)
               {
                   if (parentNode.NextNode != null)
                   {
                       e.Graphics.DrawLine(p, parentNode.Bounds.X -
parentNodeLeftDistance, top, parentNode.Bounds.X - parentNodeLeftDistance,
top + height);
                   }
                   parentNode = parentNode.Parent;
               }
           }
           // draw checkbox
           if (e.Node.Checked)
           {
               ControlPaint.DrawCheckBox(e.Graphics, new
Rectangle(nodeleft - checkboxwidth - checknodespace, top + (height -
checkboxwidth) / 2, checkboxwidth, checkboxwidth), ButtonState.Checked);
           }
           else
           {
               ControlPaint.DrawCheckBox(e.Graphics, new
Rectangle(nodeleft - checkboxwidth - checknodespace, top + (height -
checkboxwidth) / 2, checkboxwidth, checkboxwidth), ButtonState.Normal);
           }
           // erase the previous node text
           using (Brush b = new SolidBrush(this.treeView1.BackColor))
           {
               e.Graphics.DrawString(e.Node.Text, this.treeView1.Font, b,
nodeleft, nodetop);
           }
           // draw node text and highlight rectangle
           if (e.Node.IsSelected)
           {
               ControlPaint.DrawFocusRectangle(e.Graphics, e.Node.Bounds);
             
               e.Graphics.FillRectangle(Brushes.LightSkyBlue, new
Rectangle(nodeleft + 1, nodetop + 1, nodewidth - 2, nodeheight - 2));
               using (Brush b = new SolidBrush(Color.White))
               {
                   e.Graphics.DrawString(e.Node.Text, this.treeView1.Font,
b, nodeleft, nodetop);
               }
           }
           else
           {
               using (Brush b = new SolidBrush(this.treeView1.ForeColor))
               {
                   e.Graphics.DrawString(e.Node.Text, this.treeView1.Font,
b, nodeleft, nodetop);
               }
           }          
       }
}

Hope this helps.
If you have any question, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

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Hi Dieter,

How about your problem now?

If you have any question, please feel free to let me know.

Thank you for using our MSDN Managed Newsgroup Support Service!

Sincerely,
Linda Liu
Microsoft Online Community Support