<TelerikGrid Data="@MyData"
             SelectedItems="@SelectedItems"
             SelectedItemsChanged="@((IEnumerable<SampleData> items) => SelectedItemsChanged(items))"

...
    public void SelectedItemsChanged(IEnumerable<SampleData> items)
    {
        SelectedItems = items.Where(x => x.Selectable).ToList();
    }

<TelerikGrid Data="@MyData"
...
             OnRowRender="@OnRowRenderHandler">

    void OnRowRenderHandler(GridRowRenderEventArgs args)
    {
        var item = args.Item as SampleData;

        if (!item.Selectable)
        {
            args.Class = "unselectable-row";
        }
    }

<style>
    .unselectable-row > td .k-checkbox {
        opacity: 0.5;
        pointer-events: none;
    }
</style>

<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>

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

@code {
    public List<Employee> GridData { get; set; }
    IEnumerable<Employee> _selItems { get; set; }
    public IEnumerable<Employee> SelectedItems { 
        get 
        {
            return _selItems;
        } 
        set
        { 
            _selItems = value.Where(empl => empl.EmployeeId != 2);
        }
    }

    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
        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; }
    }
}

<TelerikGrid Data=@GridData
             SelectionMode="GridSelectionMode.None"
             Pageable="true"
             Height="400px">
    <GridColumns>
        <GridColumn Field="@(nameof(Employee.EmployeeId))">
            <Template>
                @{ 
                    Employee empl = context as Employee;
                    <input type="checkbox" id="@("selCb_" + empl.EmployeeId)" class="k-checkbox" checked="@empl.Selected"
                          @onchange="@(e => SelectEmployee(empl, e))" @key="@empl.EmployeeId" disabled="@( empl.EmployeeId == 3 )" />
                    <label class="k-checkbox-label" for="@("selCb_" + empl.EmployeeId)">Select @empl.EmployeeId</label>
                }
            </Template>
        </GridColumn>
        <GridColumn Field=@nameof(Employee.Name) />
        <GridColumn Field=@nameof(Employee.Team) Title="Team" />
    </GridColumns>
</TelerikGrid>

@if (SelectedItems.Count > 0)
{
    <ul>
        @foreach (Employee employee in SelectedItems)
        {
            <li>
                @employee.Name
            </li>
        }
    </ul>
}

@code {
    public List<Employee> GridData { get; set; }
    public List<Employee> SelectedItems { get; set; } = new List<Employee>();

    void SelectEmployee(Employee emplToSelect, ChangeEventArgs e)
    {
        bool isSelected = bool.Parse(e.Value.ToString());

        emplToSelect.Selected = isSelected;
        if(isSelected)
        {
            SelectedItems.Add(emplToSelect);
        }
        else
        {
            SelectedItems.Remove(emplToSelect);
        }
    }

    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
            });
        }
    }

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