WPF TreeView: A One-Level Example in C#

In this example, we will explore how to create a basic WPF TreeView that displays a one-level hierarchy of items using the `TreeView` control and .NET programming. We will use the `NodeViewModel` and `TreeViewModel` classes to define our tree structure.

The `NodeViewModel` object contains four fields: an element ID (numeric type), an element name (string type), an expand property (bool type) that determines whether the node should be expanded or collapsed at startup, and a collection of children for the item. The `TreeViewModel` class, on the other hand, has an 'Items' field to hold a collection of `NodeViewModel` objects.

To create our tree structure, we define two special classes: `TreeViewModel` and `NodeViewModel`. These classes allow us to select only a specific level of hierarchy in the relevant iteration. We also use a 'sub' datatable as an auxiliary object that has a similar structure to the 'InputDT' datatable but contains an additional 'Level' column.

During each iteration, we join the 'InputDT' datatable with the 'sub' datatable using LINQ to select rows with children for a specific level of hierarchy in subsequent iterations. We then load all data from our generic list into the 'InputDT' datatable object using a `foreach` statement.

For this example, let's assume that our 'GIER_Hierarchy_List' generic list represents a database table and its contents will be loaded into a datatable object for further processing in memory. This will serve as our source of data to populate the TreeView.

The `GIER_Hierarchy` class and the `GIER_Hierarchy_List` generic list were created solely to define some examples of hierarchical data, such as a fictional organizational company structure.

Using the code description of declared classes and objects, we can see that the main goal was to create a fully controllable TreeView UI using basic statements. To simplify the example, we replaced the database and relevant entity framework's classes with a generic list.

The presented code is designed to fill the TreeView UI with hierarchical data from a database. Each parent node can have numerous children, but a child can only have one parent. The code supports the parent/child hierarchy with one root node. The source of data is a self-referencing collection of items with the following fields: Item ID, Item Name, and Parent ID.

The code steps through all levels of the hierarchy from top to bottom and adds each item's children to its collection. Finally, it fills the WPF TreeView with multilevel hierarchical data using C#.

Wpf treeview 1 level example c