TreeListSelectionColumnHeaderTemplateContext.SelectAllEnabled Property

Determines if the Select All operation is available.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v24.1.dll

NuGet Package: DevExpress.Blazor

Declaration

public bool SelectAllEnabled { get; }

Property Value

Type	Description
Boolean	true if the Select All operation is available; otherwise, false.

Remarks

A selection column contains a checkbox in the header cell if the column’s AllowSelectAll option is enabled. You can define the column’s HeaderTemplate to display custom select elements in the header.

The Select All operation can be temporarily unavailable if you bind the TreeList to the GridDevExtremeDataSource or load data on demand. The SelectAllEnabled context parameter returns false while the Select All operation cannot be performed. Once this operation becomes available, this parameter returns true.

In the template, use the SelectAllEnabled parameter to specify the enabled or disabled state for a custom select element. In the same way, you can use the SelectEnabled parameter in the selection column’s CellDisplayTemplate.

Razor

@inject CitiesService CitiesService

<DxTreeList Data="@Data"
            KeyFieldName="ID"
            ParentKeyFieldName="ParentID"
            HasChildrenFieldName="HasChildren"
            @bind-SelectedDataItems="@SelectedDataItems">
    <Columns>
        <DxTreeListSelectionColumn>
            <HeaderTemplate>
                <DxButton Click="() => context.TreeList.SelectAllOnPage()" Text="Select All"
                          RenderStyle="ButtonRenderStyle.Link"
                          Enabled="context.SelectAllEnabled" />
            </HeaderTemplate>
        </DxTreeListSelectionColumn>
        <DxTreeListDataColumn Caption="Location" FieldName="Name" />
        <DxTreeListDataColumn FieldName="CityType" />
        <DxTreeListDataColumn FieldName="Year" DisplayFormat="d" />
        <DxTreeListDataColumn FieldName="RecordType" />
        <DxTreeListDataColumn FieldName="Population" />
    </Columns>
</DxTreeList>

@code {
    object Data { get; set; }
    IReadOnlyList<object> SelectedDataItems { get; set; }

    protected override async Task OnInitializedAsync() {
        var cities = await CitiesService.GetCitiesAsync();
        Data = new GridDevExtremeDataSource<Location>(cities.AsQueryable());
    }
}

Location.cs

public class Location {
    public string? Name { get; set; }
    public string? City { get; set; }
    public string? Country { get; set; }
    public decimal Population { get; set; }
    public int ID { get; set; }
    public int ParentID { get; set; }
    public string? CityType { get; set; }
    public string? RecordType { get; set; }
    public int? Year { get; set; }
    public bool HasChildren { get; set; }
}

CitiesService.cs

public class CitiesService {
    CitiesContext _context;
    public CitiesService(IDbContextFactory<CitiesContext> contextFactory) {
        _context = contextFactory.CreateDbContext();
    }
    public void SeedData() {
        _context.Database.EnsureCreated();
        if (_context.Locations.Any())
            return;
        var stream = File.OpenRead(@"cities.json");
        var cities = System.Text.Json.JsonSerializer.Deserialize<Location[]>(stream);
        if (cities == null)
            return;
        foreach (var city in cities) {
            city.ID++;
            city.ParentID++;
        }
        _context.Locations.AddRange(cities);
        _context.SaveChanges();
    }

    public async Task<Location[]?> GetCitiesAsync() {
        await _context.Locations.LoadAsync();
        return _context.Locations.Local.ToArray();
    }
}