Populate TreeView from DataBase

Question

I have a database table (named Topics) which includes these fields :

1. topicId
2. name
3. parentId

and by using them I wanna populate

Answer 1

Not quite.

Trees are usually handled best by not loading everything you can at once. So you need to get the root node (or topic) which has no parentIDs. Then add them to the trees root node and then for each node you add you need to get its children.

foreach (DataRow row in topicsWithOutParents.Rows)
{
   TreeNode node = New TreeNode(... whatever);
   DataSet childNodes = GetRowsWhereParentIDEquals(row["topicId"]);
   foreach (DataRow child in childNodes.Rows)
   { 
       Treenode childNode = new TreeNode(..Whatever);
       node.Nodes.add(childNode);
   }
   Tree.Nodes.Add(node);
}