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Edit Template

The column's EditTemplate defines the inline template or component that will be rendered when the user is editing the field. It is also used when inserting a new item.

You can data bind components in it to the current context, which is an instance of the model the treelist is bound to. You will need a global variable that is also an instance of the model to store those changes. The model the template receives is a copy of the original model, so that changes can be cancelled (the Cancel command).

If you need to perform logic more complex than simple data binding, use the change event of the custom editor component to perform it. You can also consider using a custom edit form outside of the treelist.

As of version 2.23.0 of Telerik UI for Blazor the TreeList row creates EditContext and passes it to the EditorTemplate. You can read more about it in the notes section of editing/overview article).

Sample edit template

@* This example shows how to use a dropdownlist to edit strings. You can implement any desired logic instead.
    If you have an enum, the treelist can edit and filter it out-of-the-box without the need for an edit template *@
@* For brevity, only Editing is implemented in this sample *@

<TelerikTreeList Data="@Data"
                 EditMode="@TreeListEditMode.Inline"
                 OnUpdate="@UpdateItem"
                 Pageable="true" ItemsField="@(nameof(Employee.DirectReports))"
                 Width="850px">
    <TreeListColumns>
        <TreeListCommandColumn Width="100px">
            <TreeListCommandButton Command="Edit" Icon="edit">Edit</TreeListCommandButton>
            <TreeListCommandButton Command="Save" Icon="save" ShowInEdit="true">Update</TreeListCommandButton>
            <TreeListCommandButton Command="Cancel" Icon="cancel" ShowInEdit="true">Cancel</TreeListCommandButton>
        </TreeListCommandColumn>

        <TreeListColumn Field="Name" Expandable="true" Width="320px" />
        <TreeListColumn Field="Role" Width="150px" Title="Position">
            <EditorTemplate>
                @{
                    CurrentlyEditedEmployee = context as Employee;
                    <TelerikDropDownList Data="@Roles" @bind-Value="@CurrentlyEditedEmployee.Role"
                                         Width="100%" PopupHeight="auto" DefaultText="Select Role...">
                    </TelerikDropDownList>
                }
            </EditorTemplate>
        </TreeListColumn>
        <TreeListColumn Field="Id" Editable="false" Width="120px" />
        <TreeListColumn Field="EmailAddress" Width="220px" />
        <TreeListColumn Field="HireDate" Width="220px" />
    </TreeListColumns>
</TelerikTreeList>

@code {
    List<Employee> Data { get; set; }
    static List<string> Roles { get; set; }
    Employee CurrentlyEditedEmployee { get; set; }

    // Sample CUD operations for the local data
    async Task UpdateItem(TreeListCommandEventArgs args)
    {
        var item = args.Item as Employee;

        // perform actual data source operations here through your service
        await MyService.Update(item);

        // update the local view-model data with the service data
        await GetTreeListData();
    }


    // sample model

    public class Employee
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Role { get; set; }
        public string EmailAddress { get; set; }
        public DateTime HireDate { get; set; }

        public List<Employee> DirectReports { get; set; }
        public bool HasChildren { get; set; }

        // Used for the editing so replacing the object in the view-model data
        // will treat it as the same object and keep its state - otherwise it will
        // collapse after editing is done, which is not what the user would expect
        public override bool Equals(object obj)
        {
            if (obj is Employee)
            {
                return this.Id == (obj as Employee).Id;
            }
            return false;
        }
    }

    // data generation

    async Task GetTreeListData()
    {
        Data = await MyService.Read();
        Roles = await MyService.GetRoles();
    }

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

    // the following static class mimics an actual data service that handles the actual data source
    // replace it with your actual service through the DI, this only mimics how the API can look like and works for this standalone page
    public static class MyService
    {
        private static List<Employee> _data { get; set; } = new List<Employee>();
        private static List<string> Roles = new List<string> { "Manager", "Employee", "Contractor" };
        // used in this example for data generation and retrieval for CUD operations on the current view-model data
        private static int LastId { get; set; } = 1;

        public static async Task<List<string>> GetRoles()
        {
            return await Task.FromResult(Roles);
        }

        public static async Task<List<Employee>> Read()
        {
            if (_data.Count < 1)
            {
                for (int i = 1; i < 15; i++)
                {
                    Employee root = new Employee
                    {
                        Id = LastId,
                        Name = $"root: {i}",
                        Role = Roles[i % Roles.Count],
                        EmailAddress = $"{i}@example.com",
                        HireDate = DateTime.Now.AddYears(-i),
                        DirectReports = new List<Employee>(),
                        HasChildren = true
                    };
                    _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}",
                            Role = Roles[j % Roles.Count],
                            EmailAddress = $"{currId}@example.com",
                            HireDate = DateTime.Now.AddDays(-currId),
                            DirectReports = new List<Employee>(),
                            HasChildren = true
                        };
                        root.DirectReports.Add(firstLevelChild);
                        LastId++;

                        for (int k = 1; k < 3; k++)
                        {
                            int nestedId = LastId;
                            firstLevelChild.DirectReports.Add(new Employee
                            {
                                Id = LastId,
                                Name = $"second level child {k} of {j} and {i}",
                                Role = Roles[k % Roles.Count],
                                EmailAddress = $"{nestedId}@example.com",
                                HireDate = DateTime.Now.AddMinutes(-nestedId)
                            }); ;
                            LastId++;
                        }
                    }
                }
            }

            return await Task.FromResult(_data);
        }

        public static async Task Update(Employee itemToUpdate)
        {
            UpdateItemRecursive(_data, itemToUpdate);
        }

        // sample helper methods for handling the view-model data hierarchy
        static void UpdateItemRecursive(List<Employee> items, Employee itemToUpdate)
        {
            for (int i = 0; i < items.Count; i++)
            {
                if (items[i].Id.Equals(itemToUpdate.Id))
                {
                    items[i] = itemToUpdate;
                    return;
                }

                if (items[i].DirectReports?.Count > 0)
                {
                    UpdateItemRecursive(items[i].DirectReports, itemToUpdate);
                }
            }
        }
    }
}

The result from the code snippet above, after Edit was clicked on the row with ID 4, and the user expanded the dropdown from the template

See Also

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