Question

I’m using this code from the another web:

How can I model this class in a database?

I have in each objective record a field named “Rank”. It tells me what position is. For instance:

Objective "Geometry": Rank1
|_Objective "Squares": Rank1
|_Objective "Circles": Rank2
|_Objective "Triangle": Rank3
  |_Objective "Types": Rank1
Objective "Algebra": Rank2
Objective "Trigonometry": Rank3

That rank tells me the order of the nodes. But I want to get all the rank:

Objective "Geometry": Rank1
|_Objective "Squares": Rank1   -> 1.1
|_Objective "Circles": Rank2
|_Objective "Triangle": Rank3
  |_Objective "Types": Rank1   -> 1.3.1
Objective "Algebra": Rank2
Objective "Trigonometry": Rank3    -> 3

I’m using LINQ to SQL.

<TreeView Name="treeView1">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate DataType="{x:Type data:Objective}" ItemsSource="{Binding Path=Objectives}" >
            <TextBlock Text="{Binding Name}" />
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

I need a linq function where I can get a specified node. I mean, a function which gets the node through the level (1.2), (1.3.1)

If exists, return the node, if not null.

UPDATE 1:

This is not really a function, but I realized it’s better to create a getNode function.

    private void AddButton_Click(object sender, RoutedEventArgs e)
    {
        NorthwindDataContext cd = new NorthwindDataContext();

        int[] levels = LevelTextBox.Text.ToIntArray('.');
        string newGroupName = NameTextBox.Text;

        Objective currentObjective = null;
        int? identity = null;

        for (int i = 0; i < levels.Length - 1; i++ )
        {
            int currentRank = levels[i];

            if (identity == null)
            {
                currentObjective = (from p in cd.Objective
                                    where p.Level == currentRank && p.Parent_ObjectiveID == null
                                    select p).SingleOrDefault();
            }
            else
            {
                currentObjective = (from p in cd.Objective
                                    where p.Level == currentRank && p.Parent_ObjectiveID == identity
                                    select p).SingleOrDefault();
            }

            if (currentObjective == null)
            {
                MessageBox.Show("Levels don't exist");
                return;
            }
            else
            {
                identity = currentObjective.ObjectiveID;
            }
        }

        if (currentObjective != null)
        {
            if (levels.Last() == currentObjective.Level)
            {
                MessageBox.Show("Level already exists");
                return;
            }
        }
        else
        {
            var aux = (from p in cd.Objective
                       where p.Parent_ObjectiveID == null && p.Level == levels.Last()
                       select p).SingleOrDefault();

            if (aux != null)
            {
                MessageBox.Show("Level already exists");
                return;
            }
        }

        var newObjective = new Objective();
        newObjective.Name = NameTextBox.Text;
        newObjective.Level = levels.Last();
        newObjective.Parent_ObjectiveID = currentObjective == null ? null : (int?)currentObjective.ObjectiveID ;

        cd.Objective.InsertOnSubmit(newObjective);
        cd.SubmitChanges();
   }

UPDATE 2:

    public Objective GetNode(params int[] indexes)
    {
        return GetNode(null, 0, indexes);
    }

    public Objective GetNode(int? parentid, int level, params int[] indexes)
    {
        NorthwindDataContext cd = new NorthwindDataContext();
        Objective item = null;

        if (indexes.Length == 0)
            return null;

        if (parentid == null)
        {
            item = (from p in cd.Objective
                    where p.Level == indexes[level] && p.Parent_ObjectiveID == null
                    select p).SingleOrDefault();

        }
        else
        {
            item = (from p in cd.Objective
                    where p.Level == indexes[level] && p.Parent_ObjectiveID == parentid
                    select p).SingleOrDefault();
        }

        if (item == null)
            return null;

        if (++level < indexes.Length)
            item = GetNode(item.ObjectiveID, level, indexes);

        return item;
    }

Answer 1

Edit:

You’re probably best to pass in an instance of the NorthwindDataContext versus creating a new one with each pass.

You could do this by creating a method as below, which has been refactored so that it doesn’t need to be recursive which should help a little in the readability department.

    public Objective GetNode(IEnumerable<Objective> collection, params int[] indices)
    {
        Objective current = null;

        for (int t = 0; t < indices.Length; t++)
        {
            Objective item = collection.SingleOrDefault(x => x.Parent == current && x.Rank == indices[t] - 1);

            if (item == null)
                return null;
        }

        return current;
    }

To be called like: GetNode(cd.Objective, LevelTextBox.Text.ToIntArray());

---

Original:
You could use something like this, it’s just a simple Extension method:

    public static TreeViewItem Get(this TreeView tree, params int[] indexes)
    {
        if (tree == null)
            return null;

        if (indexes == null || indexes.Length == 0)
            return null;

        TreeViewItem i = tree.Items[indexes[0] - 1] as TreeViewItem;

        for (int index = 1; index < indexes.Length; index++)
        {
            i = i.Items.Count >= indexes[index] - 1 ? i.Items[indexes[index] - 1] as TreeViewItem : null;

            if (i == null)
                return null;
        }

        return i;
    }

And would be used by treeView1.Get(1,3,1); or in the case of your edit, treeView1.Get(LevelTextBox.Text.Split('.').Select(x => int.Parse(x)).ToArray()); however, this has zero error handling for invalid input.

If you can’t be certain that all the items will be TreeViewItem objects, you can replace the tree.Items[...] with tree.ItemContainerGenerator.ContainerFromIndex(...) (and same with i.Items

These changes will require the TreeView to have been rendered fully, however.