Question

I have a large result set assembled in a parent/child relationship. I need to walk the tree and display the results to the user.

I’ve done this before using recursion, but because my result set may be large, I want to avoid the possibility of receiving a StackOverflowException.

I found the following example on MSDN which uses a Stack. The problem I’m having is because a stack is last-in first-out, my data doesn’t appear properly. I’d like it to look like the following:

 LeveL 1 Level 1.1 Level 1.1.1  Level 1.1.2  Level 1.2  Level 1.2.1  Level 1.2.2 

But it looks like:

 LeveL 1 Level 1.2  Level 1.2.2  Level 1.2.1  Level 1.1  Level 1.1.2  Level 1.1.1  

Any ideas?

Here is an example of my code. Assuming the DataTable dt has the following columns: ID, ParentID, and Text

    private struct Item     {         public string Text;         public int ID;         public int ParentID;     }      private void BuildView()     {         Stack<Item> itemTree = new Stack<Item>(40);          //Get All Parent Nodes         DataView dv = new DataView(dt);         dv.RowFilter = 'ParentID = 0';          //Add the parent nodes to the stack         foreach (DataRowView drv in dv)         {             Item item = new Item();             item.Text = drv['Text'].ToString();             item.ID = drv['ID'].ToString();             item.ParentID = drv['ParentID'].ToString();             itemTree.Push(item);         }          //Go through the stack one node at a time         while (itemTree.Count > 0)         {             Item currentItem = itemTree.Pop();             Debug.WriteLine(currentItem.Text);              //Get children of current node             dv.RowFilter = String.Format('ParentID = {0}', currentItem.ID);             if (dv.Count > 0)             {                 //Add child nodes to the stack                 foreach (DataRowView drvChild in dv)                 {                     Item item = new Item();                     item.Text = drvChild['Text'].ToString();                     item.ID = drvChild['ID'].ToString();                     item.ParentID = drvChild['ParentID'].ToString();                     itemTree.Push(item);                 }             }         }      } 

Answer 1

Push your items onto the stack in the reverse order, i.e. 2 before 1.

Example:

// suppose I want to push children[] onto the stack  for (int i = children.Length - 1; i >= 0; i--) {    stack.Push(children[i]); } 

To do this in your code, try the following for-each statement:

foreach (DataRowView drvChild in dv.Reverse())