Selected value: @selectedValue
<br />

<TelerikDropDownList Data="@myDdlData" TextField="MyTextField" ValueField="MyValueField" @bind-Value="selectedValue">
    <DropDownListSettings>
        <DropDownListPopupSettings MaxHeight="50px" />
    </DropDownListSettings>
</TelerikDropDownList>

@code {
    //in a real case, the model is usually in a separate file
    //the model type and value field type must be provided to the dropdpownlist
    public class MyDdlModel
    {
        public int MyValueField { get; set; }
        public string MyTextField { get; set; }
    }

    int selectedValue { get; set; }

    IEnumerable<MyDdlModel> myDdlData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x });
}

<style>
    .limited-height {
        max-height: 100px;
    }
</style>

Selected value: @selectedValue
<br />

<TelerikDropDownList Data="@myDdlData" TextField="MyTextField" ValueField="MyValueField" @bind-Value="selectedValue"
                     PopupHeight="" PopupClass="limited-height">
</TelerikDropDownList>

@code {
    //in a real case, the model is usually in a separate file
    //the model type and value field type must be provided to the dropdpownlist
    public class MyDdlModel
    {
        public int MyValueField { get; set; }
        public string MyTextField { get; set; }
    }

    int selectedValue { get; set; }

    //Define a preselected value when the component initializes
    protected override void OnInitialized()
    {
        selectedValue = 3;
    }

    IEnumerable<MyDdlModel> myDdlData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x });
}