DxTreeView.DataMappings Property

Specifies data mappings.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v24.2.dll

NuGet Package: DevExpress.Blazor

Declaration

[Parameter]
public RenderFragment DataMappings { get; set; }

Property Value

Type	Description
RenderFragment	A UI fragment to be rendered as TreeView nodes.

Remarks

You can populate the TreeView component with items from a data source.

Follow the steps below to bind TreeView to data:

1. Use the Data property to specify a data source. You can use different collection types:

   • Flat data (a collection of items organized as a single-level structure)
   • Hierarchical data (a collection of nested nodes)

2. Add the DataMappings tag to the component’s markup.

3. Create the DxTreeViewDataMapping instance and map node properties (HasChildren, IconCssClass, and so on) to data source fields. Mappings are used to assign data from the source collection to the component’s data model.

   • For flat data collections, use the Key and ParentKey properties to create a hierarchy of items. If the TreeView’s structure is linear, you can omit these properties.

   • For hierarchical data collections, the Children property is required to build the data model.

   You can create multiple DxTreeViewDataMapping instances to specify different mappings for different nesting levels. Use the Level property to specify the node level for which data mappings are applied.

View Example: TreeView for Blazor - How to load child nodes on demand (lazy loading)

Flat Data

The following code snippet binds the TreeView to the collection of flat data items. It specifies mappings for the Text, Key, and ParentKey properties.

Razor

@if(Data == null) {
    <p><em>Loading...</em></p>
} else {
    <div class="cw-320">
        <DxTreeView Data="@Data"
        @* ... *@
                    AnimationType="LayoutAnimationType.Slide">
            <DataMappings>
                <DxTreeViewDataMapping Text="Name"
                                       Key="Id"
                                       ParentKey="CategoryId"/>
            </DataMappings>
        </DxTreeView>
    </div>
}

@code {
    List<FlatDataItem> Data { get; set; }

    protected override void OnInitialized() {
        IEnumerable<ProductFlat> products = ProductData.Products;
        IEnumerable<ProductCategory> productSubcategories = ProductData.Categories;

        Data = new List<FlatDataItem>(Enum.GetValues<ProductCategoryMain>().Select(i => new FlatDataItem() { Name = i.ToString(), Id = i }));
        Data.AddRange(products.Select(i => new FlatDataItem() { Name = i.ProductName, Id = i.Id, CategoryId = i.ProductCategoryId }));
        Data.AddRange(productSubcategories.Select(i => new FlatDataItem() { Name = i.Subcategory, Id = i.SubcategoryID, CategoryId = i.Category }));
    }

}

FlatDataItem.cs

namespace BlazorDemo.Data {
    public class FlatDataItem {
        public string Name { get; set; }
        public object Id { get; set; }
        public object CategoryId { get; set; }
    }
}

Run Demo: TreeView - Binding to Flat Data

Hierarchical Data

The following code snippet binds the TreeView to the collection of ChemicalElementGroup objects. Each object can have child objects. The code specifies the Children and Text mappings to adjust the TreeView data model to the specified data source.

Razor

<DxTreeView Data="@ChemicalElements.Groups"
@* ... *@
            AnimationType="LayoutAnimationType.Slide">
    <DataMappings>
        <DxTreeViewDataMapping Children="Groups"
                               Text="Name"/>
    </DataMappings>
</DxTreeView>

ChemicalElements.cs

using System;
using System.Collections.Generic;

namespace BlazorDemo.Data {
    public static class ChemicalElements {
        private static readonly Lazy<List<ChemicalElementGroup>> chemicalElementGroups = new Lazy<List<ChemicalElementGroup>>(() => {
            List<ChemicalElementGroup> groups = new List<ChemicalElementGroup>() {
                new ChemicalElementGroup("Metals", new List<ChemicalElementGroup>() {
                    new ChemicalElementGroup("Alkali metals"),
                    new ChemicalElementGroup("Alkaline earth metals"),
                    new ChemicalElementGroup("Inner transition elements", new List<ChemicalElementGroup>() {
                        new ChemicalElementGroup("Lanthanides"),
                        new ChemicalElementGroup("Actinides")
                    }),
                    new ChemicalElementGroup("Transition elements"),
                    new ChemicalElementGroup("Other metals")
                }),
                new ChemicalElementGroup("Metalloids"),
                new ChemicalElementGroup("Nonmetals", new List<ChemicalElementGroup>() {
                    new ChemicalElementGroup("Halogens"),
                    new ChemicalElementGroup("Noble gases"),
                    new ChemicalElementGroup("Other nonmetals")
                })
            };
            return groups;
        });

        public static List<ChemicalElementGroup> Groups { get { return chemicalElementGroups.Value; } }
    }
}

Run Demo: TreeView - Binding to Hierarchical Data Watch Video: Data Binding in Navigation Components