DxTreeList.GetColumns() Method

Returns a collection of all treelist columns.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v25.1.dll

NuGet Package: DevExpress.Blazor

Declaration

public IReadOnlyList<ITreeListColumn> GetColumns()

Returns

Type	Description
IReadOnlyList<ITreeListColumn>	The column collection.

Remarks

Call the TreeList’s GetVisibleColumns() method to get a collection of visible columns sorted based on their display order. To get a collection of all treelist columns, call the GetColumns method. Whenever these methods encounter a band, they include it followed by all its nested columns in the collection. If nested bands exist, the methods add them and their nested columns recursively.

The GetDataColumns() method allows you to get a collection of data columns.

The following code snippet shows the difference between the results of the GetColumns and GetVisibleColumns methods.

Razor

@inject EmployeeTaskService EmployeeTaskService

<style>
    .my-button {
        width: 150px;
        margin-bottom: 5px;
        margin-top: 5px;
    }
</style>

<DxTreeList @ref="@TreeList"
            Data="TreeListData"
            KeyFieldName="Id"
            ParentKeyFieldName="ParentId"
            @bind-SelectedDataItems="@SelectedDataItems">
    <Columns>
        <DxTreeListDataColumn FieldName="EmployeeName" VisibleIndex="2" />
        <DxTreeListDataColumn FieldName="Name" VisibleIndex="1" />
        <DxTreeListDataColumn FieldName="StartDate" />
        <DxTreeListDataColumn FieldName="DueDate" />
        <DxTreeListSelectionColumn VisibleIndex="0" Width="50"/>
    </Columns>
</DxTreeList>

<DxButton Click="@OnGetColumns" CssClass="my-button" Text="Get Columns" />
<DxButton Click="@OnGetVisibleColumns" CssClass="my-button" Text="Get Visible Columns" />

<div><b>Columns</b>: @ColumnInfo</div>
<div><b>Visible Columns</b>: @VisibleColumnInfo</div>

@code {
    List<EmployeeTask> TreeListData { get; set; }
    ITreeList TreeList { get; set; }
    string ColumnInfo { get; set; }
    string VisibleColumnInfo { get; set; }
    IReadOnlyList<object> SelectedDataItems { get; set; }

    protected override void OnInitialized() {
        TreeListData = EmployeeTaskService.GenerateData();
    }
    void OnGetColumns() {
        ColumnInfo = GetColumnInfo(TreeList.GetColumns());
    }
    void OnGetVisibleColumns() {
        VisibleColumnInfo = GetColumnInfo(TreeList.GetVisibleColumns());
    }
    string GetColumnInfo(IEnumerable<ITreeListColumn> columns) {
        var columnInfo = columns.Select((column, index) => (1 + index) + " - " + column switch {
            ITreeListDataColumn dataColumn => dataColumn.FieldName,
            ITreeListSelectionColumn => "Selection Column",
            _ => null
        });
        return string.Join("; ", columnInfo);
    }
}

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

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), 14),
            new EmployeeTask(2, 1, "Prepare Financial Reports", "Samantha Bright", new DateTime(2018, 4, 3), new DateTime(2018, 4, 7), 17),
            new EmployeeTask(3, 1, "Prepare Marketing Plan", "Arthur Miller", new DateTime(2018, 4, 7), new DateTime(2018, 4, 14), 11),
            new EmployeeTask(4, 0, "Create Action Plan to Improve Customer Engagement", "Robert Reagan", new DateTime(2017, 8, 8), new DateTime(2018, 4, 8), 23),
            new EmployeeTask(5, 4, "Update Personnel Files", "Greta Sims", new DateTime(2017, 8, 8), new DateTime(2017, 10, 18), 100),
            new EmployeeTask(6, 4, "Review Health Insurance Options", "Brett Wade", new DateTime(2017, 9, 27), new DateTime(2017, 11, 10), 37),
            new EmployeeTask(7, 4, "Choose Between PPO and HMO Health Plan", "Sandra Johnson", new DateTime(2017, 12, 13), new DateTime(2018, 3, 23), 17),
            new EmployeeTask(8, 4, "Update Google Adwords Strategy", "Ed Holmes", new DateTime(2017, 8, 23), new DateTime(2017, 12, 23), 45),
            new EmployeeTask(9, 4, "Create New Brochure Design", "Barb Banks", new DateTime(2018, 1, 3), new DateTime(2018, 3, 14), 17),
            new EmployeeTask(10, 4, "Obtain Price Quote for New Brochure", "Kevin Carter", new DateTime(2018, 2, 1), new DateTime(2018, 3, 15), 18),
            new EmployeeTask(11, 4, "Brochure Design Review", "Cindy Stanwick", new DateTime(2017, 8, 22), new DateTime(2017, 10, 28), 4),
            new EmployeeTask(12, 4, "Review Website Redesign Strategy", "Sammy Hill", new DateTime(2017, 9, 16), new DateTime(2018, 3, 6), 73),
            new EmployeeTask(13, 4, "Roll Out New Website", "Davey Jones", new DateTime(2017, 11, 7), new DateTime(2018, 2, 6), 9),
            new EmployeeTask(14, 4, "Update Sales/Marketing Strategy", "Victor Norris", new DateTime(2017, 12, 13), new DateTime(2018, 4, 2), 5),
            new EmployeeTask(15, 4, "Update Sales/Revenue Report", "Mary Stern", new DateTime(2017, 12, 25), new DateTime(2018, 4, 2), 4),
            new EmployeeTask(16, 4, "Direct vs Online Sales Comparison Report", "Robin Cosworth", new DateTime(2018, 1, 2), new DateTime(2018, 3, 20), 14),
            new EmployeeTask(17, 4, "Review Sales Report and Approve Modifications", "Kelly Rodriguez", new DateTime(2017, 9, 4), new DateTime(2017, 10, 30), 8),
            new EmployeeTask(18, 4, "Update R&D Strategy", "James Anderson", new DateTime(2017, 11, 13), new DateTime(2017, 12, 4), 12),
            new EmployeeTask(19, 4, "Discuss Updated R&D Strategy", "Antony Remmen", new DateTime(2017, 10, 29), new DateTime(2017, 12, 31), 14),
            new EmployeeTask(20, 4, "Update QA Strategy", "Olivia Peyton", new DateTime(2017, 10, 31), new DateTime(2017, 11, 2), 18),
            new EmployeeTask(21, 4, "Schedule Training Events", "Taylor Riley", new DateTime(2017, 11, 19), new DateTime(2018, 4, 7), 21),
            new EmployeeTask(22, 4, "Approve Hiring of John Jeffers", "Amelia Harper", new DateTime(2018, 1, 7), new DateTime(2018, 4, 8), 10),
            new EmployeeTask(23, 0, "Increase Average Subscription Price", "Wally Hobbs", new DateTime(2017, 8, 9), new DateTime(2017, 9, 13), 96),
            new EmployeeTask(24, 23, "Update Non-Compete Agreements", "Brad Jameson", new DateTime(2017, 8, 9), new DateTime(2017, 9, 3), 96),
            new EmployeeTask(25, 23, "Update Employee Records with New NDA", "Karen Goodson", new DateTime(2017, 8, 23), new DateTime(2018, 9, 10), 100)
        };
    }
}

Program.cs

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

Implements

GetColumns()