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Get the parent item when inserting a child to the TreeList

Environment

Product TreeList for Blazor
Version 2.18.0 and later

Description

When inserting a child item in the TreeList I would like to be able to get the information for the parent it belongs to and show it to the user.

Solution

The approaches to handle this would depend of the type of data the component is bound to - Flat or Hierarchical. The examples below showcase how to handle both scenarios:

Get the Parent Item When Inserting a Child to the TreeList When Bound To Flat Data

Step by step Explanations

  1. Create a custom command to initiate inserting in the TreeListCommandColumn.
  2. Pass the TreeListCommandEventsArgs object to the OnClick handler.
  3. Use the TreeList state and its InsertedItem field to populate the desired information from the current item that you have in the event arguments.
@using Telerik.DataSource;

<TelerikTreeList Data="@Data"
                 EditMode="@TreeListEditMode.Popup"
                 IdField="Id"
                 ParentIdField="ParentId"
                 Pageable="true"
                 Width="850px"
                 Height="400px"
                 @ref="@TreeListRef">
    <TreeListColumns>
        <TreeListCommandColumn Width="100px">
            <TreeListCommandButton Command="MyAdd" 
                                   OnClick="@( (TreeListCommandEventArgs args) => AddItem(args) )"
                                   Icon="@IconName.Plus">
                                    Add Child
            </TreeListCommandButton>
            <TreeListCommandButton Command="Edit" Icon="@IconName.Edit">Edit</TreeListCommandButton>
            <TreeListCommandButton Command="Save" Icon="@IconName.Save" ShowInEdit="true">Update</TreeListCommandButton>
            <TreeListCommandButton Command="Cancel" Icon="@IconName.Cancel" ShowInEdit="true">Cancel</TreeListCommandButton>
        </TreeListCommandColumn>

        <TreeListColumn Field="Name" Expandable="true" Width="320px" />
        <TreeListColumn Field="Id" Width="120px" />
        <TreeListColumn Field="ParentId" Width="120px">
            <EditorTemplate>
                @{
                    CurrentlyEditedEmployee = context as Employee;
                    // One way to get the parent item from the Data based on the ID we provide, you can change as necessary 
                    Employee parent = Data.Where(x => x.Id == CurrentlyEditedEmployee.ParentId).FirstOrDefault();
                    <label>@parent.Name</label>
                }
            </EditorTemplate>
        </TreeListColumn>
        <TreeListColumn Field="EmailAddress" Width="120px" />
        <TreeListColumn Field="HireDate" Width="220px" />
    </TreeListColumns>
</TelerikTreeList>

@code {
    public TelerikTreeList<Employee> TreeListRef { get; set; }

    public void AddItem(TreeListCommandEventArgs args)
    {
        var parentId = (args.Item as Employee).ParentId;
        Employee itemToInsert = new Employee();
        itemToInsert.ParentId = parentId; // and/or other metadata
        var state = new TreeListState<Employee>();
        state.InsertedItem = itemToInsert;
        TreeListRef?.SetState(state);
    }

    public List<Employee> Data { get; set; }
    public Employee CurrentlyEditedEmployee { get; set; }

    protected override async Task OnInitializedAsync()
    {
        Data = await GetTreeListData();
    }

    // sample model

    public class Employee
    {
        // denote the parent-child relationship between items
        public int Id { get; set; }
        public int? ParentId { get; set; }

        // custom data fields for display
        public string Name { get; set; }
        public string EmailAddress { get; set; }
        public DateTime HireDate { get; set; }
    }

    // data generation

    async Task<List<Employee>> GetTreeListData()
    {
        List<Employee> data = new List<Employee>();

        for (int i = 1; i < 15; i++)
        {
            data.Add(new Employee
            {
                Id = i,
                ParentId = null, // indicates a root-level item
                Name = $"root: {i}",
                EmailAddress = $"{i}@example.com",
                HireDate = DateTime.Now.AddYears(-i)
            }); ;

            for (int j = 1; j < 4; j++)
            {
                int currId = i * 100 + j;
                data.Add(new Employee
                {
                    Id = currId,
                    ParentId = i,
                    Name = $"first level child {j} of {i}",
                    EmailAddress = $"{currId}@example.com",
                    HireDate = DateTime.Now.AddDays(-currId)
                });

                for (int k = 1; k < 3; k++)
                {
                    int nestedId = currId * 1000 + k;
                    data.Add(new Employee
                    {
                        Id = nestedId,
                        ParentId = currId,
                        Name = $"second level child {k} of {i} and {currId}",
                        EmailAddress = $"{nestedId}@example.com",
                        HireDate = DateTime.Now.AddMinutes(-nestedId)
                    }); ;
                }
            }
        }

        return await Task.FromResult(data);
    }
}

Get the Parent Item When Inserting a Child to the TreeList When Bound To Hierarchical Data

Step by step Explanations

  1. Create a custom command to initiate inserting in the TreeListCommandColumn.
  2. Pass the TreeListCommandEventsArgs object to the OnClick handler.
  3. Set the ParentItem field of the TreeList state to the item received from the TreeListCommandEventsArgs.
  4. Use the TreeList state and its InsertedItem field to populate the desired information from the current item that you have in the event arguments..
@* One way to get metadata in the current item about its parent upon insertion *@

<TelerikTreeList Data="@Data"
                 EditMode="@TreeListEditMode.Popup"
                 ItemsField="@(nameof(Employee.DirectReports))"
                 Pageable="true" 
                 Width="850px" 
                 @ref="@TreeListRef">
    <TreeListColumns>
        <TreeListCommandColumn Width="100px">
            <TreeListCommandButton Command="MyAdd"
                                   OnClick="@( (TreeListCommandEventArgs args) => AddItem(args) )"
                                   Icon="@IconName.Plus">
                                    Add Child
            </TreeListCommandButton>
            <TreeListCommandButton Command="Edit" Icon="@IconName.Edit">Edit</TreeListCommandButton>
            <TreeListCommandButton Command="Save" Icon="@IconName.Save" ShowInEdit="true">Update</TreeListCommandButton>
            <TreeListCommandButton Command="Cancel" Icon="@IconName.Cancel" ShowInEdit="true">Cancel</TreeListCommandButton>
        </TreeListCommandColumn>

        <TreeListColumn Field="Name" Expandable="true" Width="320px" />
        <TreeListColumn Field="Id" Editable="false" Width="120px" />
        <TreeListColumn Width="120px" Title="Parent Data">
            <EditorTemplate>
             @{
                    var parent = context as Employee;
                    // One way to get the parent item from the Data based on the ID we provide, you can change as necessary 
                    <label>@parent.ParentData</label>
                } change as necessary 
            </EditorTemplate>
        </TreeListColumn>
        <TreeListColumn Field="EmailAddress" Width="220px" />
        <TreeListColumn Field="HireDate" Width="220px" />
    </TreeListColumns>
</TelerikTreeList>

@code {
    TelerikTreeList<Employee> TreeListRef { get; set; }

    void AddItem(TreeListCommandEventArgs args)
    {
        Employee currItem = args.Item as Employee;
        var state = new TreeListState<Employee>();
        var itemToInsert = new Employee();
        itemToInsert.ParentData = $"Parent: {currItem.Name}"; // and/or other metadata
        state.ParentItem = currItem;
        state.InsertedItem = itemToInsert;
        TreeListRef?.SetState(state);
    }

    public List<Employee> Data { get; set; }

    // sample model

    public class Employee
    {
        // hierarchical data collections
        public List<Employee> DirectReports { get; set; }

        public string ParentData { get; set; }

        // data fields for display
        public int Id { get; set; }
        public string Name { get; set; }
        public string EmailAddress { get; set; }
        public DateTime HireDate { get; set; }
    }

    // data generation

    // used in this example for data generation and retrieval for CUD operations on the current view-model data
    public int LastId { get; set; } = 1;

    protected override async Task OnInitializedAsync()
    {
        Data = await GetTreeListData();
    }

    async Task<List<Employee>> GetTreeListData()
    {
        List<Employee> data = new List<Employee>();

        for (int i = 1; i < 15; i++)
        {
            Employee root = new Employee
            {
                Id = LastId,
                Name = $"root: {i}",
                EmailAddress = $"{i}@example.com",
                HireDate = DateTime.Now.AddYears(-i),
                DirectReports = new List<Employee>(), // prepare a collection for the child items, will be populated later in the code
            };
            data.Add(root);
            LastId++;

            for (int j = 1; j < 4; j++)
            {
                int currId = LastId;
                Employee firstLevelChild = new Employee
                {
                    Id = currId,
                    Name = $"first level child {j} of {i}",
                    EmailAddress = $"{currId}@example.com",
                    HireDate = DateTime.Now.AddDays(-currId),
                    DirectReports = new List<Employee>(), // collection for child nodes
                };
                root.DirectReports.Add(firstLevelChild); // populate the parent's collection
                LastId++;

                for (int k = 1; k < 3; k++)
                {
                    int nestedId = LastId;
                    // populate the parent's collection
                    firstLevelChild.DirectReports.Add(new Employee
                    {
                        Id = LastId,
                        Name = $"second level child {k} of {j} and {i}",
                        EmailAddress = $"{nestedId}@example.com",
                        HireDate = DateTime.Now.AddMinutes(-nestedId)
                    }); ;
                    LastId++;
                }
            }
        }

        return await Task.FromResult(data);
    }
}
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