Selected value: @myDdlData.ToList().Where(x => x.Id == selectedValueId).FirstOrDefault()?.MyValueField.ToString("MM/dd/yyyy HH:mm:ss.fff")
<br />

<TelerikDropDownList Data="@myDdlData" 
                     TextField="MyTextField" 
                     ValueField="Id" 
                     @bind-Value="selectedValueId">
</TelerikDropDownList>

@code {
    public class MyDdlModel
    {
        public int Id { get; set; }
        public DateTime MyValueField { get; set; }
        public string MyTextField => MyValueField.ToString("MM/dd/yyyy HH:mm:ss.fff"); // Display formatted DateTime
    }

    private int selectedValueId { get; set; } = 1;

    private IEnumerable<MyDdlModel> myDdlData = GenerateRandomDateTimes(20);

    private static IEnumerable<MyDdlModel> GenerateRandomDateTimes(int count)
    {
        Random random = new Random();
        DateTime startDate = DateTime.Now;

        return Enumerable.Range(1, count)
            .Select(x => new MyDdlModel
            {
                Id = x, // Unique integer Id
                MyValueField = startDate.AddDays(x)
                    .AddMinutes(random.Next(0, 60))
                    .AddSeconds(random.Next(0, 60))
                    .AddMilliseconds(random.Next(0, 1000))
            }).ToList();
    }
}

<div style="display: flex; gap: 2em;">
    <div>
        <TelerikButtonGroup SelectionMode="@ButtonGroupSelectionMode.Single">
            <ButtonGroupToggleButton @bind-Selected="@UseOnChange">Use OnChange</ButtonGroupToggleButton>
            <ButtonGroupToggleButton @bind-Selected="@UseOnClose">Use OnClose</ButtonGroupToggleButton>
        </TelerikButtonGroup>

        <TelerikDropDownList Data="@Data"
                             @bind-Value="@Value"
                             ValueField="@nameof(SampleModel.Text)"
                             OnChange="@OnDropDownListChange"
                             OnClose="@OnDropDownListClose"
                             Width="160px" />

    </div>
    <div>
        <TelerikButton OnClick="@( () => CloseLog = string.Empty )">Clear Event Log</TelerikButton>
        <p>
            <pre>@CloseLog</pre>
        </p>
    </div>
</div>

@code {
    private List<SampleModel> Data { get; set; } = new();

    private string Value { get; set; } = string.Empty;
    private List<string> Values { get; set; } = new();

    private string CloseLog { get; set; } = string.Empty;

    private bool UseOnClose { get; set; } = true;
    private bool UseOnChange { get; set; }

    [CascadingParameter]
    public DialogFactory? TelerikDialogs { get; set; }

    private async Task OnDropDownListChange(object currentValue)
    {
        CloseLog += $"OnChange {DateTime.Now.ToString("HH:mm:ss.fff")} \n";

        if (UseOnChange)
        {
            await TelerikDialogs!.AlertAsync("OnChange");
        }
    }

    private async Task OnDropDownListClose(DropDownListCloseEventArgs args)
    {
        CloseLog += $"OnClose {DateTime.Now.ToString("HH:mm:ss.fff")} \n";

        if (UseOnClose)
        {
            await TelerikDialogs!.AlertAsync("OnClose");
        }
    }

    public class SampleModel
    {
        public int Id { get; set; }
        public string Text { get; set; } = string.Empty;
    }
}