DxTreeList.ChildrenLoading Event

Allows you to populate a node with child nodes. The TreeList component raises this event for each node during initialization.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v24.2.dll

NuGet Package: DevExpress.Blazor

Declaration

[Parameter]
public Action<TreeListChildrenLoadingEventArgs> ChildrenLoading { get; set; }

Parameters

Type	Description
TreeListChildrenLoadingEventArgs	An object that contains data for this event.

Remarks

If your hierarchical data source does not include a field that stores child nodes, you can populate the TreeList component with data during component initialization. Follow the steps below to populate the component with data in code:

1. Bind the Data parameter to a C# property.
2. Populate this property with root data items in the OnInitialized or OnInitializedAsync lifecycle method.
3. Handle the ChildrenLoading event. In the event handler, use the Parent event argument to determine the processed node and assign the node’s children to the Children collection.

Note

The TreeList component loads all data during initialization when you handle the ChildrenLoading event. Instead of this event, you can handle the ChildrenLoadingOnDemand event and load nodes on demand. Refer to the following topic for more information: Load Data on Demand.

The following example populates the TreeList component with data in code:

Razor

@inject SpaceObjectDataProvider SpaceObjectDataProvider

<DxTreeList Data="TreeListData" ChildrenLoading="OnChildrenLoading">
    <Columns>
        <DxTreeListDataColumn FieldName="Name" />
        <DxTreeListDataColumn FieldName="TypeOfObject" Caption="Type" />
        <DxTreeListDataColumn FieldName="Mass10pow21kg" Caption="Mass, kg" DisplayFormat="N2">
            <HeaderCaptionTemplate>Mass, 10<sup>21</sup> &#215; kg</HeaderCaptionTemplate>
        </DxTreeListDataColumn>
        <DxTreeListDataColumn FieldName="MeanRadiusInKM" Caption="Radius, km" DisplayFormat="N2"/>
        <DxTreeListDataColumn FieldName="Volume10pow9KM3" DisplayFormat="N2">
            <HeaderCaptionTemplate>Volume, 10<sup>9</sup> &#215; km<sup>3</sup></HeaderCaptionTemplate>
        </DxTreeListDataColumn>
        <DxTreeListDataColumn FieldName="SurfaceGravity" DisplayFormat="N2">
            <HeaderCaptionTemplate>Gravity, m/s<sup>2</sup></HeaderCaptionTemplate>
        </DxTreeListDataColumn>
    </Columns>
</DxTreeList>

@code {
    object TreeListData { get; set; }

    protected override async Task OnInitializedAsync() {
        TreeListData = SpaceObjectDataProvider.GenerateRootData();
    }

    void OnChildrenLoading(TreeListChildrenLoadingEventArgs e) {
        e.Children = SpaceObjectDataProvider.GetChildren((SpaceObject)e.Parent);
    }
}

SpaceObject

using System.Collections.Generic;

public class SpaceObject {
    public string Name { get; set; }
    public double MeanRadiusInKM { get; set; }
    public double Volume10pow9KM3 { get; set; }
    public double Mass10pow21kg { get; set; }
    public double Density { get; set; }
    public double SurfaceGravity { get; set; }
    public string TypeOfObject { get; set; }
    public List<SpaceObject> Satellites { get; set; }
    public SpaceObject(
        string name,
        double meanRadiusInKM,
        double volume10pow9KM3,
        double mass10pow21kg,
        double density,
        double surfaceGravity,
        string typeOfObject,
        List<SpaceObject> satellites = null
    ) {
        Name = name;
        MeanRadiusInKM = meanRadiusInKM;
        Volume10pow9KM3 = volume10pow9KM3;
        Mass10pow21kg = mass10pow21kg;
        Density = density;
        SurfaceGravity = surfaceGravity;
        TypeOfObject = typeOfObject;
        Satellites = satellites ?? new List<SpaceObject>();
    }
}

SpaceObjectDataProvider

public class SpaceObjectDataProvider {

    public List<SpaceObject> GetChildren(SpaceObject spaceObject) {
        switch(spaceObject.Name) {
            case "Sun":
                return new List<SpaceObject>() {
                    new SpaceObject("Mercury", 2439.7, 60.83, 330.2, 5.43, 3.7, "Planet"),
                    new SpaceObject("Venus", 6051.8, 928.43, 4868.5, 5.24, 8.872, "Planet"),
                    new SpaceObject("Earth", 6371.0, 1083.21, 5973.6, 5.515, 9.78033, "Planet"),
                    new SpaceObject("Mars", 3390.0, 163.18, 641.85, 3.94, 3.7, "Planet"),
                    new SpaceObject("Jupiter", 69911, 1431280, 1898600, 1.33, 24.79, "Planet"),
                    new SpaceObject("Saturn", 58232, 827130, 568460, 0.70, 10.445, "Planet"),
                    new SpaceObject("Uranus", 25362, 68340, 86832, 1.30, 8.87, "Planet"),
                    new SpaceObject("Neptune", 24622, 62540, 102430, 1.76, 11.15, "Planet"),
                    new SpaceObject("Eris", 1170, 7, 16.7, 2.25, 0.662, "Dwarf planet"),
                    new SpaceObject("Pluto", 1153, 7.15, 13.105, 2.0, 0.61, "Dwarf planet"),
                    new SpaceObject("Makemake", 710, 1.8, 3, 2.0, 0.4,  "Dwarf planet"),
                    new SpaceObject("Haumea", 575, 1.3, 4.006, 3, 0.44, "Dwarf planet"),
                    new SpaceObject("Ceres", 475, 0.437, 0.95, 2.08, 0.27, "Dwarf planet"),
                    new SpaceObject("Pallas", 266, 0.078, 0.211, 2.8, 0.2, "Asteroid"),
                    new SpaceObject("Vesta", 264.6, 0.078, 0.262, 3.42, 0.251, "Asteroid")
                };
            case "Earth":
                return new List<SpaceObject>() {
                    new SpaceObject("Moon", 1737.1, 21.958, 73.5, 3.3464, 1.625, "Satellite")
                };
            case "Jupiter":
                return new List<SpaceObject>() {
                    new SpaceObject("Ganymede", 2631.2, 76.30, 148.2, 1.936, 1.428, "Satellite"),
                    new SpaceObject("Callisto", 2410.3, 58.65, 107.6, 1.83, 1.23603, "Satellite"),
                    new SpaceObject("Io", 1821.5, 25.32, 89.3, 3.528, 1.797, "Satellite"),
                    new SpaceObject("Europa", 1561, 15.93, 48, 3.01, 1.316, "Satellite")
                };
            case "Saturn":
                return new List<SpaceObject>() {
                    new SpaceObject("Titan", 2576, 71.52, 134.5, 1.88, 1.354, "Satellite"),
                    new SpaceObject("Rhea", 764.4, 1.87, 2.3166, 1.23, 0.26, "Satellite"),
                    new SpaceObject("Iapetus", 736, 1.55, 1.9739, 1.08, 0.223, "Satellite"),
                    new SpaceObject("Dione", 561.6, 0.73, 1.096, 1.48, 0.232, "Satellite"),
                    new SpaceObject("Tethys", 533, 0.624, 0.6173, 1.15, 0.145, "Satellite"),
                    new SpaceObject("Enceladus", 252.1, 0.067, 0.108, 1.61, 0.111, "Satellite"),
                    new SpaceObject("Mimas", 198.3, 0.033, 0.03749, 1.15, 0.06363, "Satellite")
                };
            case "Uranus":
                return new List<SpaceObject>() {
                    new SpaceObject("Titania", 788.9, 2.06, 3.526, 1.72, 0.378, "Satellite"),
                    new SpaceObject("Oberon", 761.4, 1.85, 3.014, 1.63, 0.347, "Satellite"),
                    new SpaceObject("Umbriel", 584.7, 0.84, 1.2, 1.4, 0.234, "Satellite"),
                    new SpaceObject("Ariel", 578.9, 0.81, 1.35, 1.67, 0.269, "Satellite"),
                    new SpaceObject("Miranda", 235.8, 0.055, 0.0659, 1.20, 0.07910375, "Satellite")
                };
            case "Neptune":
                return new List<SpaceObject>() {
                    new SpaceObject("Triton", 1353.4, 10.38, 21.5, 2.061, 0.782, "Satellite"),
                    new SpaceObject("Proteus", 210, 0.038, 0.050, 1.3, 0.0666, "Satellite")
                };
            default:
                return new List<SpaceObject>();
        }
    }

    public List<SpaceObject> GenerateRootData() {
        return new List<SpaceObject>() {
            new SpaceObject("Sun", 696000, 1412000000, 1989100000, 1.409, 274.0, "Star")
        };
    }
}

Program.cs

// ...
builder.Services.AddSingleton<SpaceObjectDataProvider>();