<TelerikComboBox Data="@myDdlData" 
                 TextField="MyTextField" 
                 ValueField="MyValueField" 
                 Value="selectedValue" 
                 ValueChanged="@((int? id) => ValueChangedHandler(id))" 
                 FilterOperator="StringFilterOperator.Contains"
                 Filterable="true">
</TelerikComboBox>

@code {
    private List<MyDdlModel> myDdlData { get; set; }

    private void ValueChangedHandler(int? id)
    {
        selectedValue = id;
    }

    public class MyDdlModel
    {
        public int? MyValueField { get; set; }
        public string MyTextField { get; set; }
    }

    int? selectedValue { get; set; }

    protected override void OnInitialized()
    {
        myDdlData = new List<MyDdlModel>()
        {
            new MyDdlModel()
            {
                MyValueField = 1,
                MyTextField = "John Smith"
            },
            new MyDdlModel()
            {
                MyValueField = 2,
                MyTextField = "John Smith"
            },
            new MyDdlModel()
            {
                MyValueField = 3,
                MyTextField = "John Smith"
            },
            new MyDdlModel()
            {
                MyValueField = 4,
                MyTextField = "Alice Jones"
            },
            new MyDdlModel()
            {
                MyValueField = 5,
                MyTextField = "Alice Jones"
            },
        };
    }
}