DxTreeListSelectionColumn.HeaderTemplate Property

Specifies a template for the selection column header.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v24.1.dll

NuGet Package: DevExpress.Blazor

Declaration

[Parameter]
public RenderFragment<TreeListSelectionColumnHeaderTemplateContext> HeaderTemplate { get; set; }

Property Value

Type	Description
RenderFragment<TreeListSelectionColumnHeaderTemplateContext>	The selection column’s header template.

Remarks

A selection column allows users to select and deselect rows. When the SelectionMode property is set to TreeListSelectionMode.Multiple (the default value), the selection column displays checkboxes. A user can click the checkbox in the header cell to select or deselect all rows on the current page.

You can define the HeaderTemplate to display custom content in the selection column header. Use the template’s context parameter to access the SelectionColumn and TreeList objects. The parameter’s Selected property specifies whether rows on the current page are selected.

The following code snippet displays the custom Select All button in the selection column header:

Razor

@inject EmployeeTaskService EmployeeTaskService

<DxTreeList @ref="MyTreeList"
            Data="TreeListData"
            KeyFieldName="Id"
            ParentKeyFieldName="ParentId"
            @bind-SelectedDataItems="@SelectedDataItems">
    <Columns>
        <DxTreeListSelectionColumn>
            <HeaderTemplate>
                <DxButton Click="() => MyTreeList.SelectAllOnPage()" Text="Select All"
                          RenderStyle="ButtonRenderStyle.Link" />
            </HeaderTemplate>
        </DxTreeListSelectionColumn>
        <DxTreeListDataColumn FieldName="Name" Caption="Task" />
        <DxTreeListDataColumn FieldName="EmployeeName" />
        <DxTreeListDataColumn FieldName="StartDate" />
        <DxTreeListDataColumn FieldName="DueDate" />
    </Columns>
</DxTreeList>

@code {
    List<EmployeeTask> TreeListData { get; set; }
    IReadOnlyList<object> SelectedDataItems { get; set; }
    ITreeList MyTreeList { get; set; }

    protected override void OnInitialized() {
        TreeListData = EmployeeTaskService.GenerateData();
    }
}

EmployeeTask.cs

public class EmployeeTask{
    public int Id { get; set; }
    public int ParentId { get; set; }
    public string Name { get; set; }
    public string EmployeeName { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime DueDate { get; set; }

    public EmployeeTask(
        int id,
        int parentId,
        string name,
        string employeeName,
        DateTime startDate,
        DateTime dueDate
    )
    {
        Id = id;
        ParentId = parentId;
        Name = name;
        EmployeeName = employeeName;
        StartDate = startDate;
        DueDate = dueDate;
    }
}

EmployeeTaskService.cs

public class EmployeeTaskService {
    public List<EmployeeTask> GenerateData() {
        return new List<EmployeeTask>() {
            new EmployeeTask(1, 0, "Simplify & Clarify Product Messaging", "John Heart", new DateTime(2018, 4, 3), new DateTime(2018, 4, 14)),
            new EmployeeTask(2, 1, "Prepare Financial Reports", "Samantha Bright", new DateTime(2018, 4, 3), new DateTime(2018, 4, 7)),
            new EmployeeTask(3, 1, "Prepare Marketing Plan", "Arthur Miller", new DateTime(2018, 4, 7), new DateTime(2018, 4, 14)),
            new EmployeeTask(4, 0, "Create Action Plan To Improve Customer Engagement", "Robert Reagan", new DateTime(2017, 8, 8), new DateTime(2018, 4, 8)),
            new EmployeeTask(5, 4, "Update Personnel Files", "Greta Sims", new DateTime(2017, 8, 8), new DateTime(2017, 10, 18)),
            new EmployeeTask(6, 4, "Review Health Insurance Options ", "Brett Wade", new DateTime(2017, 9, 27), new DateTime(2017, 11, 10)),
            new EmployeeTask(7, 4, "Choose Between PPO And HMO Health Plan", "Sandra Johnson", new DateTime(2017, 12, 13), new DateTime(2018, 3, 23)),
            new EmployeeTask(8, 4, "Update Google Adwords Strategy", "Ed Holmes", new DateTime(2017, 8, 23), new DateTime(2017, 12, 23)),
            new EmployeeTask(9, 4, "Create New Brochure Design", "Barb Banks", new DateTime(2018, 1, 3), new DateTime(2018, 3, 14)),
            new EmployeeTask(10, 4, "Obtain Price Quote For New Brochure", "Kevin Carter", new DateTime(2018, 2, 1), new DateTime(2018, 3, 15)),
            new EmployeeTask(11, 4, "Brochure Design Review", "Cindy Stanwick", new DateTime(2017, 8, 22), new DateTime(2017, 10, 28)),
            new EmployeeTask(12, 4, "Review Website Re-Design Strategy", "Sammy Hill", new DateTime(2017, 9, 16), new DateTime(2018, 3, 6)),
            new EmployeeTask(13, 4, "Rollout New Website", "Davey Jones", new DateTime(2017, 11, 7), new DateTime(2018, 2, 6)),
            new EmployeeTask(14, 4, "Update Sales/Marketing Strategy", "Victor Norris", new DateTime(2017, 12, 13), new DateTime(2018, 4, 2)),
            new EmployeeTask(15, 4, "Update Sales/Revenue Report", "Mary Stern", new DateTime(2017, 12, 25), new DateTime(2018, 4, 2)),
            new EmployeeTask(16, 4, "Direct Vs Online Sales Comparison Report", "Robin Cosworth", new DateTime(2018, 1, 2), new DateTime(2018, 3, 20)),
            new EmployeeTask(17, 4, "Review Sales Report and Approve Modifications", "Kelly Rodriguez", new DateTime(2017, 9, 4), new DateTime(2017, 10, 30)),
            new EmployeeTask(18, 4, "Update R&D Strategy", "James Anderson", new DateTime(2017, 11, 13), new DateTime(2017, 12, 4)),
            new EmployeeTask(19, 4, "Discuss Updated R&D Strategy", "Antony Remmen", new DateTime(2017, 10, 29), new DateTime(2017, 12, 31)),
            new EmployeeTask(20, 4, "Update QA Strategy", "Olivia Peyton", new DateTime(2017, 10, 31), new DateTime(2017, 11, 2)),
            new EmployeeTask(21, 4, "Schedule Training Events", "Taylor Riley", new DateTime(2017, 11, 19), new DateTime(2018, 4, 7)),
            new EmployeeTask(22, 4, "Approve The Hiring Of John Jeffers", "Amelia Harper", new DateTime(2018, 1, 7), new DateTime(2018, 4, 8)),
            new EmployeeTask(23, 0, "Increase Average Subscription Price ", "Wally Hobbs", new DateTime(2017, 8, 9), new DateTime(2017, 9, 13)),
            new EmployeeTask(24, 23, "Update Non-Compete Agreements", "Brad Jameson", new DateTime(2017, 8, 9), new DateTime(2017, 9, 3)),
            new EmployeeTask(25, 23, "Update Employee Records With New NDA", "Karen Goodson", new DateTime(2017, 8, 23), new DateTime(2018, 9, 10))
        };
    }
}

Program.cs

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

For more information, refer to the following topic: Templates in Blazor TreeList.

Implements

HeaderTemplate