How To Load Data On Demand Using Command In Winui Treegrid?

Updated on Jan 16, 2026

This example describes how to load data on demand using command in WinUI TreeGrid (SfTreeGrid).

Load on demand using command

SfTreeGrid allows you to load child items only when they are requested to load on-demand. Initially populate the root Nodes by assigning SfTreeGrid.ItemsSource and then when any node is expanded, child items can be loaded using SfTreeGrid.LoadOnDemandCommand.

XAML

<treeGrid:SfTreeGrid Name="treeGrid"
                    LoadOnDemandCommand="{Binding CommandLoad}"
                    AutoGenerateColumns="True"
                    ItemsSource="{Binding EmployeeDetails}" >
    <treeGrid:SfTreeGrid.DataContext>
        <local:ViewModel />
    </treeGrid:SfTreeGrid.DataContext>
</treeGrid:SfTreeGrid>

C

class LoadCommand : ICommand
{
    public event EventHandler CanExecuteChanged;
    MainPage page;
    public bool CanExecute(object parameter)
    {
        TreeNode node = (parameter as TreeNode);
        EmployeeInfo emp = node.Item as EmployeeInfo;
        if (emp != null)
            if (emp.ReportsTo == -1 || emp.ReportsTo == 34 || emp.ReportsTo == 36 || emp.ReportsTo == 65)
                return true;
        return false;
    }

    public void Execute(object parameter)
    {
        TreeNode node = (parameter as TreeNode);
        page = new MainPage();
        EmployeeInfo emp = node.Item as EmployeeInfo;
        if (emp != null)
        {
            node.PopulateChildNodes((page.DataContext as ViewModel).GetReportees(emp.ID));
        }
    }

    event EventHandler<object> ICommand.CanExecuteChanged
    {
        add
        {
            throw new NotImplementedException();
        }

        remove
        {
            throw new NotImplementedException();
        }
    }
}

Handling expander visibility

TreeGrid shows the expander for a particular node based on return value of CanExecute method of LoadOnDemandCommand. If CanExecute returns true, then expander icon is displayed for that node. If CanExecute returns false, then expander icon will not displayed for that node. CanExecute method gets called to decide the visibility of expander icon and before executing LoadOnDemandCommand.

public bool CanExecute(object parameter)
{
    TreeNode node = (parameter as TreeNode);
    EmployeeInfo emp = node.Item as EmployeeInfo;
    if (emp != null)
        if (emp.ReportsTo == -1 || emp.ReportsTo == 34 || emp.ReportsTo == 36 || emp.ReportsTo == 65)
            return true;
    return false;
}

On-demand loading of child items

You can load child items for the node in Execute method of LoadOnDemandCommand. Execute method will get called when user expands the tree node. In execute method, you can populate the child nodes by calling TreeNode.PopulateChildNodes method by passing the child items collection.

MainPage page;

public void Execute(object parameter)
{
    TreeNode node = (parameter as TreeNode);
    page = new MainPage();
    EmployeeInfo emp = node.Item as EmployeeInfo;
    if (emp != null)
    {
        node.PopulateChildNodes((page.DataContext as ViewModel).GetReportees(emp.ID));
    }
}