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TreeView duplicating root nodes, despite there being a single root in Nodes array

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0

I'm currently using TreeView to display a file tree for visualising diffs for a source control project. I have a "Diff" method that recursively edits an existing node in the root "Nodes" array in the TreeView, and then updates the tree afterward.

However, I've encountered an issue where the root node will duplicate for seemingly no reason, despite the debugger telling me there's a single element in the "Nodes" array at the very root of the TreeView, with no indication of an error.

I've already attempted to use "Nodes.Clear()" and then re-add the offending node, however even when clearing the array, the duplicate persists, (even when Nodes.Count is 0). I've also tried using BeginUpdate() and EndUpdate(), but to no avail.

Here's an MCVE:

public partial class BrokenControl : TreeView

 public BrokenControl()
 
 InitializeComponent();
 

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 Nodes[0] = RecursiveEdit(Nodes[0]);
 Update();
 

 //This function simply recursively edits the Nodes array.
 int iterations = 10;
 private TreeNode RecursiveEdit(TreeNode node)
 
 node.Nodes.Add(iterations.ToString());
 iterations--;
 if (iterations<=0)
 
 return node;
 

 RecursiveEdit(node.Nodes[0]);
 return node;
 

As mentioned, I only expect there to be a single node on the TreeView when it's updated, but instead I get a duplicate node containing duplicated contents of the first.

c# .net winforms

share|improve this question

edited Mar 25 at 9:59

Larry Tang

asked Mar 25 at 9:42

Larry TangLarry Tang

1341212 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  This is a debugging problem Navigate through code with the Visual Studio debugger
  
  – TheGeneral
  Mar 25 at 9:46
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is a UserControl with type TreeView, "Nodes" is a default property of the class, not my own variable. Apologies for the lack of explanation. docs.microsoft.com/en-us/dotnet/api/…
  
  – Larry Tang
  Mar 25 at 10:00
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Put a breakpoint on lines containing the text Nodes.Add (all of them). Run the code. How many times (in total) do those breakpoints get hit?
  
  – mjwills
  Mar 25 at 10:09
  

  
  
  
  

add a comment | 

0

I'm currently using TreeView to display a file tree for visualising diffs for a source control project. I have a "Diff" method that recursively edits an existing node in the root "Nodes" array in the TreeView, and then updates the tree afterward.

However, I've encountered an issue where the root node will duplicate for seemingly no reason, despite the debugger telling me there's a single element in the "Nodes" array at the very root of the TreeView, with no indication of an error.

I've already attempted to use "Nodes.Clear()" and then re-add the offending node, however even when clearing the array, the duplicate persists, (even when Nodes.Count is 0). I've also tried using BeginUpdate() and EndUpdate(), but to no avail.

Here's an MCVE:

public partial class BrokenControl : TreeView

 public BrokenControl()
 
 InitializeComponent();
 

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 Nodes[0] = RecursiveEdit(Nodes[0]);
 Update();
 

 //This function simply recursively edits the Nodes array.
 int iterations = 10;
 private TreeNode RecursiveEdit(TreeNode node)
 
 node.Nodes.Add(iterations.ToString());
 iterations--;
 if (iterations<=0)
 
 return node;
 

 RecursiveEdit(node.Nodes[0]);
 return node;
 

As mentioned, I only expect there to be a single node on the TreeView when it's updated, but instead I get a duplicate node containing duplicated contents of the first.

c# .net winforms

share|improve this question

edited Mar 25 at 9:59

Larry Tang

asked Mar 25 at 9:42

Larry TangLarry Tang

1341212 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  This is a debugging problem Navigate through code with the Visual Studio debugger
  
  – TheGeneral
  Mar 25 at 9:46
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is a UserControl with type TreeView, "Nodes" is a default property of the class, not my own variable. Apologies for the lack of explanation. docs.microsoft.com/en-us/dotnet/api/…
  
  – Larry Tang
  Mar 25 at 10:00
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Put a breakpoint on lines containing the text Nodes.Add (all of them). Run the code. How many times (in total) do those breakpoints get hit?
  
  – mjwills
  Mar 25 at 10:09
  

  
  
  
  

add a comment | 

I'm currently using TreeView to display a file tree for visualising diffs for a source control project. I have a "Diff" method that recursively edits an existing node in the root "Nodes" array in the TreeView, and then updates the tree afterward.

However, I've encountered an issue where the root node will duplicate for seemingly no reason, despite the debugger telling me there's a single element in the "Nodes" array at the very root of the TreeView, with no indication of an error.

I've already attempted to use "Nodes.Clear()" and then re-add the offending node, however even when clearing the array, the duplicate persists, (even when Nodes.Count is 0). I've also tried using BeginUpdate() and EndUpdate(), but to no avail.

Here's an MCVE:

public partial class BrokenControl : TreeView

 public BrokenControl()
 
 InitializeComponent();
 

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 Nodes[0] = RecursiveEdit(Nodes[0]);
 Update();
 

 //This function simply recursively edits the Nodes array.
 int iterations = 10;
 private TreeNode RecursiveEdit(TreeNode node)
 
 node.Nodes.Add(iterations.ToString());
 iterations--;
 if (iterations<=0)
 
 return node;
 

 RecursiveEdit(node.Nodes[0]);
 return node;
 

As mentioned, I only expect there to be a single node on the TreeView when it's updated, but instead I get a duplicate node containing duplicated contents of the first.

c# .net winforms

share|improve this question

edited Mar 25 at 9:59

Larry Tang

asked Mar 25 at 9:42

Larry TangLarry Tang

1341212 bronze badges

public partial class BrokenControl : TreeView

 public BrokenControl()
 
 InitializeComponent();
 

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 Nodes[0] = RecursiveEdit(Nodes[0]);
 Update();
 

 //This function simply recursively edits the Nodes array.
 int iterations = 10;
 private TreeNode RecursiveEdit(TreeNode node)
 
 node.Nodes.Add(iterations.ToString());
 iterations--;
 if (iterations<=0)
 
 return node;
 

 RecursiveEdit(node.Nodes[0]);
 return node;
 

share|improve this question

edited Mar 25 at 9:59

Larry Tang

asked Mar 25 at 9:42

Larry TangLarry Tang

1341212 bronze badges

share|improve this question

edited Mar 25 at 9:59

Larry Tang

asked Mar 25 at 9:42

Larry TangLarry Tang

1341212 bronze badges

asked Mar 25 at 9:42

Larry TangLarry Tang

1341212 bronze badges

asked Mar 25 at 9:42

Larry TangLarry Tang

1341212 bronze badges

1 Answer
1

active

oldest

votes

1

I managed to fix the issue by using a workaround: instead of directly manipulating the Root node, saving a copy and editing, then clearing and readding, solved my issue.

Still do not know what was causing the dupe even when Nodes.Count was 0 and 1, however this seems to work.

Corrected MCVE:

public partial class BrokenControl : TreeView

 ...

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 TreeNode savedNode = RecursiveEdit(Nodes[0]);

 //This fixes it.
 Nodes.Clear();
 Nodes.Add(savedNode);

 Update();
 

 ...

share|improve this answer

answered Mar 25 at 10:13

Larry TangLarry Tang

1341212 bronze badges

add a comment | 

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1

I managed to fix the issue by using a workaround: instead of directly manipulating the Root node, saving a copy and editing, then clearing and readding, solved my issue.

Still do not know what was causing the dupe even when Nodes.Count was 0 and 1, however this seems to work.

Corrected MCVE:

public partial class BrokenControl : TreeView

 ...

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 TreeNode savedNode = RecursiveEdit(Nodes[0]);

 //This fixes it.
 Nodes.Clear();
 Nodes.Add(savedNode);

 Update();
 

 ...

share|improve this answer

answered Mar 25 at 10:13

Larry TangLarry Tang

1341212 bronze badges

add a comment | 

1

I managed to fix the issue by using a workaround: instead of directly manipulating the Root node, saving a copy and editing, then clearing and readding, solved my issue.

Still do not know what was causing the dupe even when Nodes.Count was 0 and 1, however this seems to work.

Corrected MCVE:

public partial class BrokenControl : TreeView

 ...

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 TreeNode savedNode = RecursiveEdit(Nodes[0]);

 //This fixes it.
 Nodes.Clear();
 Nodes.Add(savedNode);

 Update();
 

 ...

share|improve this answer

answered Mar 25 at 10:13

Larry TangLarry Tang

1341212 bronze badges

add a comment | 

I managed to fix the issue by using a workaround: instead of directly manipulating the Root node, saving a copy and editing, then clearing and readding, solved my issue.

Still do not know what was causing the dupe even when Nodes.Count was 0 and 1, however this seems to work.

Corrected MCVE:

public partial class BrokenControl : TreeView

 ...

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 TreeNode savedNode = RecursiveEdit(Nodes[0]);

 //This fixes it.
 Nodes.Clear();
 Nodes.Add(savedNode);

 Update();
 

 ...

share|improve this answer

answered Mar 25 at 10:13

Larry TangLarry Tang

1341212 bronze badges

public partial class BrokenControl : TreeView

 ...

 public void Go(object sender, EventArgs e)
 
 Nodes.Add("Root");
 TreeNode savedNode = RecursiveEdit(Nodes[0]);

 //This fixes it.
 Nodes.Clear();
 Nodes.Add(savedNode);

 Update();
 

 ...

share|improve this answer

answered Mar 25 at 10:13

Larry TangLarry Tang

1341212 bronze badges

answered Mar 25 at 10:13

Larry TangLarry Tang

1341212 bronze badges

answered Mar 25 at 10:13

Larry TangLarry Tang

1341212 bronze badges