The ASP.NET Core treeview checkbox has a tri-state mode also, which is applicable only for parent nodes. The ASP.NET Core TreeView control provides built-in support for checkboxes, allowing users to select more than one item. This is helpful in making a typical directory tree and file system. Tree node with iconsĭisplay nodes with labels and icons to present the content in a more readable format. Also, child nodes in the control can be loaded from any web services or inserted dynamically. The ASP.NET Core TreeView control has a load-on-demand option that allows you to load huge amounts of data dynamically, which improves the control’s performance. The treeview data can be local or remote data and fetched using different kinds of adaptors like OData, OData V4, URL, JSON, and Web API. You can bind data to the ASP.NET Core TreeView control from any valid data source, such as XML, JSON, and JSONP. It provides great performance with its advanced features like load on demand, checkbox support, multiple selection, tree navigation, drag and drop, tree node editing, and template support. Finally, the TreeView supports databinding, allowing you to throw a hierarchical data structure at the control so it will render properly for you.įinally, let's take a look at ASP.NET 2.0's MultiView and View controls.The ASP.NET Core TreeView control allows you to represent hierarchical data in a tree structure. You may expand and contract nodes as well. In addition to building nodes using the designer, you may build them programmatically. This is just a small illustration of what the TreeView is capable of doing. The following graphic shows how the selected details appear in the ListBox. TreeNodeCollection childNodes = įoreach(TreeNode childNode in childNodes) protected void TreeView1_SelectedNodeChanged(object sender, EventArgse) Add code to interrogate the selected node to list information about the child nodes. Then add an event handler for the SelectedNodeChanged event. Add a TextBox to show information about the selected node. Name the label LabelSelectedNode so that you have programmatic access to it. First add a label to show the selected node. To make it a bit more interesting, add some functionality to handle some of the tree node events. The following graphic shows how the TreeView appears in the browser. After running the page, take a quick look at the ASPX source code to see how the TreeView manages its nodes. You should be able to expand and contract the nodes. īuild the project and browse to the page.Īdd a border around the TreeView using the Border property.The following graphic show the TreeView node editor. In this example, the second layer of nodes represents the members of the bands, and the third layer represents their roles. You may nest these nodes as deeply as necessary. The next button over is for adding child nodes. In this example, the bands are represented as root nodes. From this dialog box you may edit each of the nodes. You may edit the nodes by right-clicking on the TreeView control and selecting Edit Nodes from the local menu. Īfter selecting a style for the TreeView, select the Edit Nodes task.The following graphic shows the local menu which you may use to bring up the AutoFormat dialog box. Browse through a few of them, highlighting them to see what the styles look like. Visual Studio presents a dialog box showing a number of styles for the TreeView. Visual Studio presents a number of options you can apply to the TreeView. You'll find it under the Navigation controls. Pick up a TreeView from the toolbox and add it to the default page. The example will illustrate the hierarchical nature of the bands mentioned by showing the name of the band followed by a list of roles performed by each particular member.īegin by adding a new Web form to the ControlPotpourri Web site. This exercise illustrates the TreeView control by showing a hierarchical, expandable list of 1970s bands that are still around today. To see how the TreeView works, let's look at an example. It's useful any time you want to represent a nested data structure and have a way of drilling down into it. If there are further subdirectories, you may open them the same way.ĪSP.NET provides this functionality via the TreeView. When you click on a plus sign, Windows Explorer displays an open folder and then shows the subdirectories directly underneath. For example, when you explore your C drive using Windows Explorer, the directories appear as closed folders with small plus signs to the left. Tree controls let users navigate hierarchies by representing expandable and collapsible nodes.
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