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    Tree List

    Load Data on Demand

    The TreeList can load a remote dataset dynamically as a user expands nodes. The dataset must have a plain structure.

    This feature requires client- and server-side configurations. To configure the client-side part, do the following:

    1. Send an expanded node's ID to the server
      For this, implement the CustomStore's load function. In this demo, we do it in the dataSource configuration object.

    2. Delegate filtering to the server
      Set the remoteOperations.filtering property to true.

    3. Specify the data field that defines whether the node has children
      Use the hasItemsExpr property to set this data field.

    Server-side implementation is available in the ASP.NET Core and ASP.NET MVC versions of this demo under the TreeListDataController.cs tab.

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    window.onload = function() { var viewModel = { treeListOptions: { dataSource: { load: function(options) { return $.ajax({ url: "https://js.devexpress.com/Demos/Mvc/api/treeListData", dataType: "json", data: { parentIds: options.parentIds.join(",") } }); } }, remoteOperations: { filtering: true }, keyExpr: "id", parentIdExpr: "parentId", hasItemsExpr: "hasItems", rootValue: "", showBorders: true, columns: [ { dataField: "name" }, { dataField: "size", width: 100, customizeText: function(e) { if(e.value !== null) { return Math.ceil(e.value / 1024) + " KB"; } } }, { dataField: "createdDate", dataType: "date", width: 150 }, { dataField: "modifiedDate", dataType: "date", width: 150 } ] } }; ko.applyBindings(viewModel, document.getElementById("treelist")); };
    <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>DevExtreme Demo</title> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0" /> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script> <script>window.jQuery || document.write(decodeURIComponent('%3Cscript src="js/jquery.min.js"%3E%3C/script%3E'))</script> <script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/21.1.6/css/dx.common.css" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/21.1.6/css/dx.light.css" /> <script src="https://cdn3.devexpress.com/jslib/21.1.6/js/dx.all.js"></script> <link rel="stylesheet" type="text/css" href="styles.css" /> <script src="index.js"></script> </head> <body class="dx-viewport"> <div class="demo-container"> <div id="treelist" data-bind="dxTreeList: treeListOptions"></div> </div> </body> </html>
    #treelist { max-height: 440px; }