@if (customPopupVisible)
{
    <div style="position: fixed; top: 0; bottom: 0; left:0; right: 0; z-index: 2;" @onclick:preventDefault @onclick="@HideItemChooser"></div>
}

<TelerikButton OnClick="@ShowItemChooser">Choose Items</TelerikButton>
<div style="position: relative;">
    <TelerikAnimationContainer Width="300px" @ref="@ItemChooser" Class="k-popup no-headers">
        <TelerikGrid Data=@GridData
                     SelectionMode="GridSelectionMode.Multiple"
                     @bind-SelectedItems="SelectedItems"
                     Pageable="true"
                     Height="400px">
            <GridColumns>
                <GridCheckboxColumn />
                <GridColumn Field=@nameof(Employee.Name) />
                <GridColumn Field=@nameof(Employee.Team) Title="Team" />
            </GridColumns>
        </TelerikGrid>
    </TelerikAnimationContainer>
</div>

@if (SelectedItems != null)
{
    <ul>
        @foreach (Employee employee in SelectedItems)
        {
            <li>
                @employee.Name
            </li>
        }
    </ul>
}

@code {
    TelerikAnimationContainer ItemChooser { get; set; }
    bool customPopupVisible { get; set; }
    async void ShowItemChooser()
    {
        customPopupVisible = true;
        await ItemChooser.ShowAsync();
    }
    async void HideItemChooser()
    {
        customPopupVisible = false;
        await ItemChooser.HideAsync();
    }

    public List<Employee> GridData { get; set; }
    public IEnumerable<Employee> SelectedItems { get; set; } = Enumerable.Empty<Employee>();

    protected override void OnInitialized()
    {
        GridData = new List<Employee>();
        for (int i = 0; i < 15; i++)
        {
            GridData.Add(new Employee()
            {
                EmployeeId = i,
                Name = "Employee " + i.ToString(),
                Team = "Team " + i % 3
            });
        }

        // select Employee with 3 through 5. Not required
        SelectedItems = GridData.Skip(2).Take(3).ToList();
    }

    public class Employee
    {
        public int EmployeeId { get; set; }
        public string Name { get; set; }
        public string Team { get; set; }
    }
}

<style>
    .no-headers .k-grid-header{
    display: none;
    }
</style>