To attempt to solve this problem, I created a sample windows form and wrote the following code. I envisioned the datatable design as follows:
NoteID NoteName ParentNoteID
"1" "One" null
"2" "Two" "1"
"3" "Three" "2"
"4" "Four" null
...
This should create a Tree as (sorry, I'm not very good with ASCII art!):
One
|
——Two
|
————Three
|
Four
Pseudocode goes like this:
- Iterate through all the rows in the datatable.
- For each row, create a TreeNode and set it's properties. Recursively repeat the process for all rows that have a ParentNodeID matching this row's ID.
- Each complete iteration returns a node that will contain all matching childnodes with infinite nesting.
- Add the completed nodelist to the TreeView.
The problem in your scenario arises from the fact the "foreign key" refers to a column in the same table. This means that when we iterate through the rows, we have to keep track of which rows have already been parsed. For example, in the table above, the node matching the second and third rows are already added in the first complete iteration. Therefore, we must not add them again. There are two ways to keep track of this:
- Maintain a list of ID's that have been done (
doneNotes). Before adding each new node, check if the noteID exists in that list. This is the faster method and should normally be preferred. (this method is commented out in the code below)
- For each iteration, use a predicate generic delegate (
FindNode) to search the list of added nodes (accounting for nested nodes) to see if the to-be added node exists in that list. This is the slower solution, but I kinda like complicated code! :P
Ok, here's the tried and tested code (C# 2.0):
public partial class TreeViewColor : Form
{
private DataTable dt;
// Alternate way of maintaining a list of nodes that have already been added.
//private List<int> doneNotes;
private static int noteID;
public TreeViewColor()
{
InitializeComponent();
}
private void TreeViewColor_Load(object sender, EventArgs e)
{
CreateData();
CreateNodes();
foreach (TreeNode rootNode in treeView1.Nodes)
{
ColorNodes(rootNode, Color.MediumVioletRed, Color.DodgerBlue);
}
}
private void CreateData()
{
dt = new DataTable("CaseNotes");
dt.Columns.Add("NoteID", typeof(string));
dt.Columns.Add("NoteName", typeof(string));
DataColumn dc = new DataColumn("ParentNoteID", typeof(string));
dc.AllowDBNull = true;
dt.Columns.Add(dc);
// Add sample data.
dt.Rows.Add(new string[] { "1", "One", null });
dt.Rows.Add(new string[] { "2", "Two", "1" });
dt.Rows.Add(new string[] { "3", "Three", "2" });
dt.Rows.Add(new string[] { "4", "Four", null });
dt.Rows.Add(new string[] { "5", "Five", "4" });
dt.Rows.Add(new string[] { "6", "Six", null });
dt.Rows.Add(new string[] { "7", "Seven", null });
dt.Rows.Add(new string[] { "8", "Eight", "7" });
dt.Rows.Add(new string[] { "9", "Nine", "8" });
}
private void CreateNodes()
{
DataRow[] rows = new DataRow[dt.Rows.Count];
dt.Rows.CopyTo(rows, 0);
//doneNotes = new List<int>(9);
// Get the TreeView ready for node creation.
// This isn't really needed since we're using AddRange (but it's good practice).
treeView1.BeginUpdate();
treeView1.Nodes.Clear();
TreeNode[] nodes = RecurseRows(rows);
treeView1.Nodes.AddRange(nodes);
// Notify the TreeView to resume painting.
treeView1.EndUpdate();
}
private TreeNode[] RecurseRows(DataRow[] rows)
{
List<TreeNode> nodeList = new List<TreeNode>();
TreeNode node = null;
foreach (DataRow dr in rows)
{
node = new TreeNode(dr["NoteName"].ToString());
noteID = Convert.ToInt32(dr["NoteID"]);
node.Name = noteID.ToString();
node.ToolTipText = noteID.ToString();
// This method searches the "dirty node list" for already completed nodes.
//if (!doneNotes.Contains(doneNoteID))
// This alternate method using the Find method uses a Predicate generic delegate.
if (nodeList.Find(FindNode) == null)
{
DataRow[] childRows = dt.Select("ParentNoteID = " + dr["NoteID"]);
if (childRows.Length > 0)
{
// Recursively call this function for all childRowsl
TreeNode[] childNodes = RecurseRows(childRows);
// Add all childnodes to this node.
node.Nodes.AddRange(childNodes);
}
// Mark this noteID as dirty (already added).
//doneNotes.Add(noteID);
nodeList.Add(node);
}
}
// Convert this List<TreeNode> to an array so it can be added to the parent node/TreeView.
TreeNode[] nodeArr = nodeList.ToArray();
return nodeArr;
}
private static bool FindNode(TreeNode n)
{
if (n.Nodes.Count == 0)
return n.Name == noteID.ToString();
else
{
while (n.Nodes.Count > 0)
{
foreach (TreeNode tn in n.Nodes)
{
if (tn.Name == noteID.ToString())
return true;
else
n = tn;
}
}
return false;
}
}
protected void ColorNodes(TreeNode root, Color firstColor, Color secondColor)
{
root.ForeColor = root.Index % 2 == 0 ? firstColor : secondColor;
foreach (TreeNode childNode in root.Nodes)
{
Color nextColor = childNode.ForeColor = childNode.Index % 2 == 0 ? firstColor : secondColor;
if (childNode.Nodes.Count > 0)
{
// alternate colors for the next node
if (nextColor == firstColor)
ColorNodes(childNode, secondColor, firstColor);
else
ColorNodes(childNode, firstColor, secondColor);
}
}
}
}
Best Answer
Finally this is what I did, it suits my requirements. I first make a copy of my TreeView and store into fieldsTreeCache. I then clear the fieldsTree. I then search through the cache and add any node containing my search parameter to the fieldsTree. Note here that once you search, you no longer have the parent nodes that show. You just get all of the end nodes. I did this because if not I had 2 choices:
Not expand the parent nodes but then you just get the categories and not the children nodes that you're searching for.