I've just started learning how to program and have been following along with this tutorial on graphs but I've run into some issues using the given
AddDirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)
It fails to build using the default from the tutorial, for example
web.AddDirectedEdge("People.aspx", "Privacy.htm"); // People -> Privacy
This gives the error "No overload for method 'AddDirectedEdge' takes 2 arguments". Adding an integer as a third argument does not help either, it just gives another error "Argument#: cannot convert from 'string' to 'GraphTest.GraphNode< string>'"
I'm not sure how to fix this, any help/insight regarding it would be appreciated. For ease of viewing the graph and graph node classes are shown below (these are all available through the above link as well):
public class GraphNode<T> : Node<T>
{
private List<int> costs;
public GraphNode() : base() { }
public GraphNode(T value) : base(value) { }
public GraphNode(T value, NodeList<T> neighbors) : base(value, neighbors) { }
new public NodeList<T> Neighbors
{
get
{
if (base.Neighbors == null)
base.Neighbors = new NodeList<T>();
return base.Neighbors;
}
}
public List<int> Costs
{
get
{
if (costs == null)
costs = new List<int>();
return costs;
}
}
}
.
public class Graph<T> : IEnumerable<T>
{
private NodeList<T> nodeSet;
public Graph() : this(null) { }
public Graph(NodeList<T> nodeSet)
{
if (nodeSet == null)
this.nodeSet = new NodeList<T>();
else
this.nodeSet = nodeSet;
}
public void AddNode(GraphNode<T> node)
{
// adds a node to the graph
nodeSet.Add(node);
}
public void AddNode(T value)
{
// adds a node to the graph
nodeSet.Add(new GraphNode<T>(value));
}
public void AddDirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)
{
from.Neighbors.Add(to);
from.Costs.Add(cost);
}
public void AddUndirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)
{
from.Neighbors.Add(to);
from.Costs.Add(cost);
to.Neighbors.Add(from);
to.Costs.Add(cost);
}
public bool Contains(T value)
{
return nodeSet.FindByValue(value) != null;
}
public bool Remove(T value)
{
// first remove the node from the nodeset
GraphNode<T> nodeToRemove = (GraphNode<T>)nodeSet.FindByValue(value);
if (nodeToRemove == null)
// node wasn't found
return false;
// otherwise, the node was found
nodeSet.Remove(nodeToRemove);
// enumerate through each node in the nodeSet, removing edges to this node
foreach (GraphNode<T> gnode in nodeSet)
{
int index = gnode.Neighbors.IndexOf(nodeToRemove);
if (index != -1)
{
// remove the reference to the node and associated cost
gnode.Neighbors.RemoveAt(index);
gnode.Costs.RemoveAt(index);
}
}
return true;
}
public NodeList<T> Nodes
{
get
{
return nodeSet;
}
}
public int Count
{
get { return nodeSet.Count; }
}
public IEnumerator<T> GetEnumerator()
{
throw new NotImplementedException();
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
throw new NotImplementedException();
}
IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
throw new NotImplementedException();
}
}
Well, obviously it is complaining about type mismatch:
you are supplying string type instead of GraphNode<T>.
Instead you should call it as:
web.AddDirectedEdge(new GraphNode("People.aspx"), new GraphNode("Privacy.htm"), 1);
where 1 is a cost, which is required, or
var ppl = new GraphNode("People.aspx");
var prv = new GraphNode("Privacy.htm");
web.AddDirectedEdge(ppl, prv, 1);
if you like to reuse nodes further in code.
As a side note, it seems you are making some trivial mistakes. Before making it further I strongly recommend you to take at least basic course of C#. There is plenty of then available for free in the Web, this for example.
I am writing a custom configuration section using the .NET configuration api. I want to define a section that can have exactly one of two sub-elements,
e.g.
<MyCustomSection>
<myItems>
<myItemType name="1">
<firstSubTypeConfig />
</myItemType>
<myItemType name="2">
<secondSubTypeConfig />
</myItemType>
</myItems>
</MyCustomSection>
Currently, I have the sections defined like:
public class MyCustomSection : ConfigurationSection
{
public override bool IsReadOnly()
{
return false;
}
[ConfigurationProperty("myItems")]
public MyItemsCollection MyItems
{
get { return (MyItemsCollection)base["myItems"]; }
set { base["myItems"] = value; }
}
}
[ConfigurationCollection(typeof(MyItemType), AddItemName="myItemType",
CollectionType=ConfigurationElementCollectionType.BasicMap)]
public class MyItemsCollection : ConfigurationElementCollection
{
public override bool IsReadOnly()
{
return false;
}
public override ConfigurationElementCollectionType CollectionType
{
get { return ConfigurationElementCollectionType.BasicMap; }
}
protected override string ElementName
{
get { return "myItemType"; }
}
protected override ConfigurationElement CreateNewElement()
{
return new MyItemType();
}
protected override object GetElementKey(ConfigurationElement element)
{
return (element as MyItemType).Name;
}
}
public class MyItemType : ConfigurationElement
{
public override bool IsReadOnly()
{
return false;
}
[ConfigurationProperty("name", IsRequired=true)]
public string Name
{
get { return (string)base["name"]; }
set { base["name"] = value; }
}
[ConfigurationProperty("firstSubTypeConfig")]
public FirstSubTypeConfig FirstSubTypeConfig
{
get { return (FirstSubTypeConfig)base["firstSubTypeConfig"]; }
set { base["firstSubTypeConfig"] = value; }
}
[ConfigurationProperty("secondSubTypeConfig")]
public SecondSubTypeConfig SecondSubTypeConfig
{
get { return (SecondSubTypeConfig)base["secondSubTypeConfig"]; }
set { base["secondSubTypeConfig"] = value; }
}
}
public class FirstSubTypeConfig : ConfigurationElement
{
public override bool IsReadOnly()
{
return false;
}
}
public class SecondSubTypeConfig : ConfigurationElement
{
public override bool IsReadOnly()
{
return false;
}
}
The configuration is also modified and saved programmatically, and currently, saving the
configuration section will add the secondSubTypeConfig element even if I only specify the
firstSubTypeConfig element.
My first thought was to introduce a common base class for FirstSubTypeConfig and SecondSubTypeConfig, but I'm not clear on if or how the configuration api would handle that.
How do I setup mutually exclusive custom config elements?
I'm not sure this is the "correct" approach, but this works.
The code as written in the question will load the config file fine. You can check the ElementInformation.IsPresent property to validate that exactly one element is included.
e.g.
var custom = (MyCustomSection)ConfigurationManager.GetSection("MyCustomSection");
foreach (MyItemType itemType in custom.MyItems)
{
if (itemType.FirstSubTypeConfig.ElementInformation.IsPresent
&& itemType.SecondSubTypeConfig.ElementInformation.IsPresent)
{
throw new ConfigurationErrorsException("At most one of firstSubTypeConfig or secondSubTypeConfig can be specified in a myItemType element");
}
else if (!itemType.FirstSubTypeConfig.ElementInformation.IsPresent
&& !itemType.SecondSubTypeConfig.ElementInformation.Ispresent)
{
throw new ConfigurationErrorsException("Either a firstSubTypeConfig or a secondSubTypeConfig element must be specified in a myItemType element");
}
}
As for saving the config, it seems that checking for ElementInformation.IsPresent and explicitly setting it to null will prevent the element from being written to the config file. e.g.
var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
var custom = (MyCustomSection)config.GetSection("MyCustomSection");
//make modifications against the custom variable ...
foreach (MyItemType itemType in custom.MyItems)
{
if (!itemType.FirstSubTypeConfig.ElementInformation.IsPresent)
itemType.FirstSubTypeConfig = null;
if (!itemType.SecondSubTypeConfig.ElementInformation.IsPresent)
itemType.SecondSubTypeConfig = null;
}
config.Save();
I think that you should do that on the PostDeserialize method ihnerited from the ConfigurationElement class without doing that on your business logic.
For example:
protected override void PostDeserialize()
{
base.PostDeserialize();
if (FirstSubTypeConfig != null && SecondTypeCOnfig != null)
{
throw new ConfigurationErrorsException("Only an element is allowed.");
}
}
I have a datasource (BindingList) with many Users, but there are some users I don't want to display in my DataGridView. Is it possible to hide them. I can't find events that works.
RowsAdded sometimes hides worng rows.
Looks like I have to implement my own filter. I build an adapter for the BindingList wich can display a filtered version of any BindingList. You just has to inherite from it. Here is my Example. I want to show only users with user.CanEdit = true
public class AhpUserFilter : FilterBindingListAdapter<AhpUser>
{
public AhpUserFilter(AhpUserCollection users)
: base(users.GetList() as IBindingList)
{
}
protected override bool ISVisible(AhpUser user)
{
return user.CanEdit;
}
}
Here is how you can bind the new List to a DatagridView:
AhpUserFilter userSource = new AhpUserFilter(users);
userSource.Filter = "yes!";
dataGridViewUser.DataSource = userSource;
Okay, the Filter property is useless, yet. But the Adapter class is very experimental yet. But for simple adding and removing with a DataGrid it seems to work well.
Here is the code for the adapter:
public class FilterBindingListAdapter<T> : BindingList<T>, IBindingListView
{
protected string filter = String.Empty;
protected IBindingList bindingList;
private bool filtering = false;
public FilterBindingListAdapter(IBindingList bindingList)
{
this.bindingList = bindingList;
DoFilter();
}
protected override void OnListChanged(ListChangedEventArgs e)
{
if (!filtering)
{
switch (e.ListChangedType)
{
case ListChangedType.ItemAdded:
bindingList.Insert(e.NewIndex, this[e.NewIndex]);
break;
}
}
base.OnListChanged(e);
}
protected override void RemoveItem(int index)
{
if (!filtering)
{
bindingList.RemoveAt(index);
}
base.RemoveItem(index);
}
protected virtual void DoFilter()
{
filtering = true;
this.Clear();
foreach (T e in bindingList)
{
if (filter.Length == 0 || this.ISVisible(e))
{
this.Add((T)e);
}
}
filtering = false;
}
protected virtual bool ISVisible(T element)
{
return true;
}
#region IBindingListView Members
public void ApplySort(ListSortDescriptionCollection sorts)
{
throw new NotImplementedException();
}
public string Filter
{
get
{
return filter;
}
set
{
filter = value;
DoFilter();
}
}
public void RemoveFilter()
{
Filter = String.Empty;
}
public ListSortDescriptionCollection SortDescriptions
{
get { throw new NotImplementedException(); }
}
public bool SupportsAdvancedSorting
{
get { return false; }
}
public bool SupportsFiltering
{
get { return true; }
}
#endregion
}
You can filter the rows with the BindingSource.Filter property. However, the built-in implementation of BindingList<T> doesn't support filtering, so you need to implement it yourself. You can find a few examples on Google. This one looks interesting...
I was looking for a tree or graph data structure in C#, but I guess there isn't one provided. An Extensive Examination of Data Structures Using C# 2.0 a bit about why. Is there a convenient library which is commonly used to provide this functionality? Perhaps through a strategy pattern to solve the issues presented in the article.
I feel a bit silly implementing my own tree, just as I would implementing my own ArrayList.
I just want a generic tree which can be unbalanced. Think of a directory tree. C5 looks nifty, but their tree structures seem to be implemented as balanced red-black trees better suited to search than representing a hierarchy of nodes.
My best advice would be that there is no standard tree data structure because there are so many ways you could implement it that it would be impossible to cover all bases with one solution. The more specific a solution, the less likely it is applicable to any given problem. I even get annoyed with LinkedList - what if I want a circular linked list?
The basic structure you'll need to implement will be a collection of nodes, and here are some options to get you started. Let's assume that the class Node is the base class of the entire solution.
If you need to only navigate down the tree, then a Node class needs a List of children.
If you need to navigate up the tree, then the Node class needs a link to its parent node.
Build an AddChild method that takes care of all the minutia of these two points and any other business logic that must be implemented (child limits, sorting the children, etc.)
delegate void TreeVisitor<T>(T nodeData);
class NTree<T>
{
private T data;
private LinkedList<NTree<T>> children;
public NTree(T data)
{
this.data = data;
children = new LinkedList<NTree<T>>();
}
public void AddChild(T data)
{
children.AddFirst(new NTree<T>(data));
}
public NTree<T> GetChild(int i)
{
foreach (NTree<T> n in children)
if (--i == 0)
return n;
return null;
}
public void Traverse(NTree<T> node, TreeVisitor<T> visitor)
{
visitor(node.data);
foreach (NTree<T> kid in node.children)
Traverse(kid, visitor);
}
}
Simple recursive implementation...
< 40 lines of code...
You just need to keep a reference to the root of the tree outside of the class,
or wrap it in another class, maybe rename to TreeNode??
Here's mine, which is very similar to Aaron Gage's, just a little more conventional, in my opinion. For my purposes, I haven't ran into any performance issues with List<T>. It would be easy enough to switch to a LinkedList if needed.
namespace Overby.Collections
{
public class TreeNode<T>
{
private readonly T _value;
private readonly List<TreeNode<T>> _children = new List<TreeNode<T>>();
public TreeNode(T value)
{
_value = value;
}
public TreeNode<T> this[int i]
{
get { return _children[i]; }
}
public TreeNode<T> Parent { get; private set; }
public T Value { get { return _value; } }
public ReadOnlyCollection<TreeNode<T>> Children
{
get { return _children.AsReadOnly(); }
}
public TreeNode<T> AddChild(T value)
{
var node = new TreeNode<T>(value) {Parent = this};
_children.Add(node);
return node;
}
public TreeNode<T>[] AddChildren(params T[] values)
{
return values.Select(AddChild).ToArray();
}
public bool RemoveChild(TreeNode<T> node)
{
return _children.Remove(node);
}
public void Traverse(Action<T> action)
{
action(Value);
foreach (var child in _children)
child.Traverse(action);
}
public IEnumerable<T> Flatten()
{
return new[] {Value}.Concat(_children.SelectMany(x => x.Flatten()));
}
}
}
Yet another tree structure:
public class TreeNode<T> : IEnumerable<TreeNode<T>>
{
public T Data { get; set; }
public TreeNode<T> Parent { get; set; }
public ICollection<TreeNode<T>> Children { get; set; }
public TreeNode(T data)
{
this.Data = data;
this.Children = new LinkedList<TreeNode<T>>();
}
public TreeNode<T> AddChild(T child)
{
TreeNode<T> childNode = new TreeNode<T>(child) { Parent = this };
this.Children.Add(childNode);
return childNode;
}
... // for iterator details see below link
}
Sample usage:
TreeNode<string> root = new TreeNode<string>("root");
{
TreeNode<string> node0 = root.AddChild("node0");
TreeNode<string> node1 = root.AddChild("node1");
TreeNode<string> node2 = root.AddChild("node2");
{
TreeNode<string> node20 = node2.AddChild(null);
TreeNode<string> node21 = node2.AddChild("node21");
{
TreeNode<string> node210 = node21.AddChild("node210");
TreeNode<string> node211 = node21.AddChild("node211");
}
}
TreeNode<string> node3 = root.AddChild("node3");
{
TreeNode<string> node30 = node3.AddChild("node30");
}
}
BONUS
See fully-fledged tree with:
iterator
searching
Java/C#
https://github.com/gt4dev/yet-another-tree-structure
The generally excellent C5 Generic Collection Library has several different tree-based data structures, including sets, bags and dictionaries. Source code is available if you want to study their implementation details. (I have used C5 collections in production code with good results, although I haven't used any of the tree structures specifically.)
See https://github.com/YaccConstructor/QuickGraph (previously http://quickgraph.codeplex.com/)
QuickGraph provides generic directed/undirected graph data structures and algorithms for .NET 2.0 and up. QuickGraph comes with algorithms such as depth-first search, breadth-first search, A* search, shortest path, k-shortest path, maximum flow, minimum spanning tree, least common ancestors, etc... QuickGraph supports MSAGL, GLEE, and Graphviz to render the graphs, serialization to GraphML, etc.
Here's my own:
class Program
{
static void Main(string[] args)
{
var tree = new Tree<string>()
.Begin("Fastfood")
.Begin("Pizza")
.Add("Margherita")
.Add("Marinara")
.End()
.Begin("Burger")
.Add("Cheese burger")
.Add("Chili burger")
.Add("Rice burger")
.End()
.End();
tree.Nodes.ForEach(p => PrintNode(p, 0));
Console.ReadKey();
}
static void PrintNode<T>(TreeNode<T> node, int level)
{
Console.WriteLine("{0}{1}", new string(' ', level * 3), node.Value);
level++;
node.Children.ForEach(p => PrintNode(p, level));
}
}
public class Tree<T>
{
private Stack<TreeNode<T>> m_Stack = new Stack<TreeNode<T>>();
public List<TreeNode<T>> Nodes { get; } = new List<TreeNode<T>>();
public Tree<T> Begin(T val)
{
if (m_Stack.Count == 0)
{
var node = new TreeNode<T>(val, null);
Nodes.Add(node);
m_Stack.Push(node);
}
else
{
var node = m_Stack.Peek().Add(val);
m_Stack.Push(node);
}
return this;
}
public Tree<T> Add(T val)
{
m_Stack.Peek().Add(val);
return this;
}
public Tree<T> End()
{
m_Stack.Pop();
return this;
}
}
public class TreeNode<T>
{
public T Value { get; }
public TreeNode<T> Parent { get; }
public List<TreeNode<T>> Children { get; }
public TreeNode(T val, TreeNode<T> parent)
{
Value = val;
Parent = parent;
Children = new List<TreeNode<T>>();
}
public TreeNode<T> Add(T val)
{
var node = new TreeNode<T>(val, this);
Children.Add(node);
return node;
}
}
Output:
Fastfood
Pizza
Margherita
Marinara
Burger
Cheese burger
Chili burger
Rice burger
I have a little extension to the solutions.
Using a recursive generic declaration and a deriving subclass, you can better concentrate on your actual target.
Notice, it’s different from a non generic implementation, you don’t need to cast 'node' to 'NodeWorker'.
Here's my example:
public class GenericTree<T> where T : GenericTree<T> // recursive constraint
{
// no specific data declaration
protected List<T> children;
public GenericTree()
{
this.children = new List<T>();
}
public virtual void AddChild(T newChild)
{
this.children.Add(newChild);
}
public void Traverse(Action<int, T> visitor)
{
this.traverse(0, visitor);
}
protected virtual void traverse(int depth, Action<int, T> visitor)
{
visitor(depth, (T)this);
foreach (T child in this.children)
child.traverse(depth + 1, visitor);
}
}
public class GenericTreeNext : GenericTree<GenericTreeNext> // concrete derivation
{
public string Name {get; set;} // user-data example
public GenericTreeNext(string name)
{
this.Name = name;
}
}
static void Main(string[] args)
{
GenericTreeNext tree = new GenericTreeNext("Main-Harry");
tree.AddChild(new GenericTreeNext("Main-Sub-Willy"));
GenericTreeNext inter = new GenericTreeNext("Main-Inter-Willy");
inter.AddChild(new GenericTreeNext("Inter-Sub-Tom"));
inter.AddChild(new GenericTreeNext("Inter-Sub-Magda"));
tree.AddChild(inter);
tree.AddChild(new GenericTreeNext("Main-Sub-Chantal"));
tree.Traverse(NodeWorker);
}
static void NodeWorker(int depth, GenericTreeNext node)
{ // a little one-line string-concatenation (n-times)
Console.WriteLine("{0}{1}: {2}", String.Join(" ", new string[depth + 1]), depth, node.Name);
}
Try this simple sample.
public class TreeNode<TValue>
{
#region Properties
public TValue Value { get; set; }
public List<TreeNode<TValue>> Children { get; private set; }
public bool HasChild { get { return Children.Any(); } }
#endregion
#region Constructor
public TreeNode()
{
this.Children = new List<TreeNode<TValue>>();
}
public TreeNode(TValue value)
: this()
{
this.Value = value;
}
#endregion
#region Methods
public void AddChild(TreeNode<TValue> treeNode)
{
Children.Add(treeNode);
}
public void AddChild(TValue value)
{
var treeNode = new TreeNode<TValue>(value);
AddChild(treeNode);
}
#endregion
}
I created a Node<T> class that could be helpful for other people. The class has properties like:
Children
Ancestors
Descendants
Siblings
Level of the node
Parent
Root
Etc.
There is also the possibility to convert a flat list of items with an Id and a ParentId to a tree. The nodes holds a reference to both the children and the parent, so that makes iterating nodes quite fast.
There is the now released .NET codebase: specifically the code for a SortedSet that implements a red-black tree: sortedset.cs
This is, however, a balanced tree structure. So my answer is more a reference to what I believe is the only native tree-structure in the .NET core library.
I've completed the code that Berezh has shared.
public class TreeNode<T> : IEnumerable<TreeNode<T>>
{
public T Data { get; set; }
public TreeNode<T> Parent { get; set; }
public ICollection<TreeNode<T>> Children { get; set; }
public TreeNode(T data)
{
this.Data = data;
this.Children = new LinkedList<TreeNode<T>>();
}
public TreeNode<T> AddChild(T child)
{
TreeNode<T> childNode = new TreeNode<T>(child) { Parent = this };
this.Children.Add(childNode);
return childNode;
}
public IEnumerator<TreeNode<T>> GetEnumerator()
{
throw new NotImplementedException();
}
IEnumerator IEnumerable.GetEnumerator()
{
return (IEnumerator)GetEnumerator();
}
}
public class TreeNodeEnum<T> : IEnumerator<TreeNode<T>>
{
int position = -1;
public List<TreeNode<T>> Nodes { get; set; }
public TreeNode<T> Current
{
get
{
try
{
return Nodes[position];
}
catch (IndexOutOfRangeException)
{
throw new InvalidOperationException();
}
}
}
object IEnumerator.Current
{
get
{
return Current;
}
}
public TreeNodeEnum(List<TreeNode<T>> nodes)
{
Nodes = nodes;
}
public void Dispose()
{
}
public bool MoveNext()
{
position++;
return (position < Nodes.Count);
}
public void Reset()
{
position = -1;
}
}
I have added a complete solution and example using the NTree class above. I also added the "AddChild" method...
public class NTree<T>
{
public T data;
public LinkedList<NTree<T>> children;
public NTree(T data)
{
this.data = data;
children = new LinkedList<NTree<T>>();
}
public void AddChild(T data)
{
var node = new NTree<T>(data) { Parent = this };
children.AddFirst(node);
}
public NTree<T> Parent { get; private set; }
public NTree<T> GetChild(int i)
{
foreach (NTree<T> n in children)
if (--i == 0)
return n;
return null;
}
public void Traverse(NTree<T> node, TreeVisitor<T> visitor, string t, ref NTree<T> r)
{
visitor(node.data, node, t, ref r);
foreach (NTree<T> kid in node.children)
Traverse(kid, visitor, t, ref r);
}
}
public static void DelegateMethod(KeyValuePair<string, string> data, NTree<KeyValuePair<string, string>> node, string t, ref NTree<KeyValuePair<string, string>> r)
{
string a = string.Empty;
if (node.data.Key == t)
{
r = node;
return;
}
}
Using it
NTree<KeyValuePair<string, string>> ret = null;
tree.Traverse(tree, DelegateMethod, node["categoryId"].InnerText, ref ret);
There is also the possibility to use XML with LINQ:
Create XML tree in C# (LINQ to XML)
XML is the most mature and flexible solution when it comes to using trees and LINQ provides you with all the tools that you need.
The configuration of your tree also gets much cleaner and user-friendly as you can simply use an XML file for the initialization.
If you need to work with objects, you can use XML serialization:
XML serialization
Most trees are formed by the data you are processing.
Say you have a person class that includes details of someone’s
parents, would you rather have the tree structure as part of your
“domain class”, or use a separate tree class that contained links to
your person objects? Think about a simple operation like getting all
the grandchildren of a person, should this code be in the person
class, or should the user of the person class have to know about a
separate tree class?
Another example is a parse tree in a compiler…
Both of these examples show that the concept of a tree is part of the domain of the data and using a separate general-purpose tree at least doubles the number of objects that are created as well as making the API harder to program again.
We want a way to reuse the standard tree operations, without having to reimplement them for all trees, while at the same time, not having to use a standard tree class. Boost has tried to solve this type of problem for C++, but I am yet to see any effect for .NET to get it adapted.
If you are going to display this tree on the GUI, you can use TreeView and TreeNode. (I suppose technically you can create a TreeNode without putting it on a GUI, but it does have more overhead than a simple homegrown TreeNode implementation.)
Here is my implementation of a BST:
class BST
{
public class Node
{
public Node Left { get; set; }
public object Data { get; set; }
public Node Right { get; set; }
public Node()
{
Data = null;
}
public Node(int Data)
{
this.Data = (object)Data;
}
public void Insert(int Data)
{
if (this.Data == null)
{
this.Data = (object)Data;
return;
}
if (Data > (int)this.Data)
{
if (this.Right == null)
{
this.Right = new Node(Data);
}
else
{
this.Right.Insert(Data);
}
}
if (Data <= (int)this.Data)
{
if (this.Left == null)
{
this.Left = new Node(Data);
}
else
{
this.Left.Insert(Data);
}
}
}
public void TraverseInOrder()
{
if(this.Left != null)
this.Left.TraverseInOrder();
Console.Write("{0} ", this.Data);
if (this.Right != null)
this.Right.TraverseInOrder();
}
}
public Node Root { get; set; }
public BST()
{
Root = new Node();
}
}
Tree With Generic Data
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
public class Tree<T>
{
public T Data { get; set; }
public LinkedList<Tree<T>> Children { get; set; } = new LinkedList<Tree<T>>();
public Task Traverse(Func<T, Task> actionOnNode, int maxDegreeOfParallelism = 1) => Traverse(actionOnNode, new SemaphoreSlim(maxDegreeOfParallelism, maxDegreeOfParallelism));
private async Task Traverse(Func<T, Task> actionOnNode, SemaphoreSlim semaphore)
{
await actionOnNode(Data);
SafeRelease(semaphore);
IEnumerable<Task> tasks = Children.Select(async input =>
{
await semaphore.WaitAsync().ConfigureAwait(false);
try
{
await input.Traverse(actionOnNode, semaphore).ConfigureAwait(false);
}
finally
{
SafeRelease(semaphore);
}
});
await Task.WhenAll(tasks);
}
private void SafeRelease(SemaphoreSlim semaphore)
{
try
{
semaphore.Release();
}
catch (Exception ex)
{
if (ex.Message.ToLower() != "Adding the specified count to the semaphore would cause it to exceed its maximum count.".ToLower())
{
throw;
}
}
}
public async Task<IEnumerable<T>> ToList()
{
ConcurrentBag<T> lst = new ConcurrentBag<T>();
await Traverse(async (data) => lst.Add(data));
return lst;
}
public async Task<int> Count() => (await ToList()).Count();
}
Unit Tests
using System.Threading.Tasks;
using Xunit;
public class Tree_Tests
{
[Fact]
public async Task Tree_ToList_Count()
{
Tree<int> head = new Tree<int>();
Assert.NotEmpty(await head.ToList());
Assert.True(await head.Count() == 1);
// child
var child = new Tree<int>();
head.Children.AddFirst(child);
Assert.True(await head.Count() == 2);
Assert.NotEmpty(await head.ToList());
// grandson
child.Children.AddFirst(new Tree<int>());
child.Children.AddFirst(new Tree<int>());
Assert.True(await head.Count() == 4);
Assert.NotEmpty(await head.ToList());
}
[Fact]
public async Task Tree_Traverse()
{
Tree<int> head = new Tree<int>() { Data = 1 };
// child
var child = new Tree<int>() { Data = 2 };
head.Children.AddFirst(child);
// grandson
child.Children.AddFirst(new Tree<int>() { Data = 3 });
child.Children.AddLast(new Tree<int>() { Data = 4 });
int counter = 0;
await head.Traverse(async (data) => counter += data);
Assert.True(counter == 10);
counter = 0;
await child.Traverse(async (data) => counter += data);
Assert.True(counter == 9);
counter = 0;
await child.Children.First!.Value.Traverse(async (data) => counter += data);
Assert.True(counter == 3);
counter = 0;
await child.Children.Last!.Value.Traverse(async (data) => counter += data);
Assert.True(counter == 4);
}
}
I don't like a tree aproach. It gets things overcomplicated including search or dril-down or even ui controls populating.
I would suggest to use a very simple approach with IDictionary<TChild, TParent>. This also allows to have no connections between nodes or levels.
In case you need a rooted tree data structure implementation that uses less memory, you can write your Node class as follows (C++ implementation):
class Node {
Node* parent;
int item; // depending on your needs
Node* firstChild; //pointer to left most child of node
Node* nextSibling; //pointer to the sibling to the right
}