populate treeview from single table parent-child relationship

  • Thread starter Thread starter Robert Samuel White via .NET 247
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Robert Samuel White via .NET 247

Hi there! I've been looking around with little luck on how topopulate a treeview from a single table parent-childrelationship. It is simply a table of users, where each areidentified with a unique UserId and have a correspondingParentId (pointing to their boss' UserId). If it's a top-leveluser, then the ParentId is set to 0. Can someone please help mefigure out the best way to populate this list? I'm unsure ofhow to do the logic behind the algorithm. Any help would begreatly appreciated.

-Samuel
 
Robert said:
Hi there! I've been looking around with little luck on how to populate a
treeview from a single table parent-child relationship. It is simply a
table of users, where each are identified with a unique UserId and have a
corresponding ParentId (pointing to their boss' UserId). If it's a
top-level user, then the ParentId is set to 0. Can someone please help me
figure out the best way to populate this list? I'm unsure of how to do the
logic behind the algorithm. Any help would be greatly appreciated.
Click to expand...

It's pretty simple: (I assume your data is in a datatable)

TreeNode rootNode = null;
Hashtable idToNode = new Hashtable(users.Rows.Count);

// first walk the list of users and create Treeview Nodes.
// we need 2 loops, as we can encounter a user with a parent
// and the parent isn't processed yet.
for(int i=0;i<users.Rows.Count;i++)
{
TreeNode newNode = new TreeNode(users.Rows["UserId"].ToString());
idToNode.Add(users.Rows["UserId"], newNode);
if((int)users.Rows["ParentId"]==0)
{
// found the root
rootNode = newNode;
}
}

// now we're going to build the tree!
for(int i=0;i<users.Rows.Count;i++)
{
TreeNode nodeToAdd = (TreeNode)idToNode[users.Rows["UserId"]];
// find parent
if((int)users.Rows["ParentId"]!=0)
{
TreeNode parentNode = (TreeNode)idToNode[users.Rows["ParentId"]];
parentNode.Nodes.Add(nodeToAdd);
}
}

// add the complete node structure to the treeview control
myTreeView.Nodes.Add(rootNode);

voila, an O(2) algo. This is from my bare head, so I might have made a syntax
error here and there, but you get the idea.

FB
 
Thanks, Frans, I was surprised to see my post in here as I did not think it
got posted (I waited a whole day before posting again) and now I've actually
got something workable. I will definitely check out your code so I can get
a real grasp on this stuff. I really appreciate you taking the time to post
this for me!


Frans Bouma said:
Robert said:
Hi there! I've been looking around with little luck on how to populate a
treeview from a single table parent-child relationship. It is simply a
table of users, where each are identified with a unique UserId and have a
corresponding ParentId (pointing to their boss' UserId). If it's a
top-level user, then the ParentId is set to 0. Can someone please help me
figure out the best way to populate this list? I'm unsure of how to do the
logic behind the algorithm. Any help would be greatly appreciated.
Click to expand...

It's pretty simple: (I assume your data is in a datatable)

TreeNode rootNode = null;
Hashtable idToNode = new Hashtable(users.Rows.Count);

// first walk the list of users and create Treeview Nodes.
// we need 2 loops, as we can encounter a user with a parent
// and the parent isn't processed yet.
for(int i=0;i<users.Rows.Count;i++)
{
TreeNode newNode = new TreeNode(users.Rows["UserId"].ToString());
idToNode.Add(users.Rows["UserId"], newNode);
if((int)users.Rows["ParentId"]==0)
{
// found the root
rootNode = newNode;
}
}

// now we're going to build the tree!
for(int i=0;i<users.Rows.Count;i++)
{
TreeNode nodeToAdd = (TreeNode)idToNode[users.Rows["UserId"]];
// find parent
if((int)users.Rows["ParentId"]!=0)
{
TreeNode parentNode = (TreeNode)idToNode[users.Rows["ParentId"]];
parentNode.Nodes.Add(nodeToAdd);
}
}

// add the complete node structure to the treeview control
myTreeView.Nodes.Add(rootNode);

voila, an O(2) algo. This is from my bare head, so I might have made a syntax
error here and there, but you get the idea.

FB
Click to expand...
 
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