When bound to a nullable GUID, the DropDownList invokes validation and shows validation messages as soon as the view loads.
Expected: the same behavior as with nullable int - validation is to be triggered by the form submission or selection from the dropdown.
Worked as expected in 1.2.0.
Reproducible:
@using Telerik.Blazor.Components.DropDownList@using System.ComponentModel.DataAnnotations<EditForm Model="@person" OnValidSubmit="@HandleValidSubmit"> <DataAnnotationsValidator /> <ValidationSummary /> <p class="gender"> Gender: <TelerikDropDownList @bind-Value="person.Gender" DefaultItem="@ddlHint" Data="@genders" TextField="MyTextField" ValueField="MyValueField"> </TelerikDropDownList> <ValidationMessage For="@(() => person.Gender)"></ValidationMessage> </p> <button type="submit">Submit</button></EditForm>@code { // Usually the model classes would be in different files public class Person { [Required(ErrorMessage = "Gender is mandatory.")]//the value field in the dropdown model must be null in the default item public Guid? Gender { get; set; } } public class MyDdlModel { //nullable so the default item can allow required field validation public Guid? MyValueField { get; set; } public string MyTextField { get; set; } } Person person = new Person(); MyDdlModel ddlHint = new MyDdlModel { MyValueField = null, MyTextField = "Gender" }; IEnumerable<MyDdlModel> genders = new List<MyDdlModel>{ new MyDdlModel {MyTextField = "female", MyValueField = new Guid()}, new MyDdlModel {MyTextField = "male", MyValueField = new Guid()}, new MyDdlModel {MyTextField = "other", MyValueField = new Guid()}, new MyDdlModel {MyTextField = "I'd rather not say", MyValueField = new Guid()} }; void HandleValidSubmit() { Console.WriteLine("OnValidSubmit"); }}
When the Value you bind to the DropDownList is null (for example, because it is a model that is not filled in by the user yet, and you need to perform validation), the component throws a null reference exception.
This does not happen for a nullable integer (example here)
Reproducible:
@using System.ComponentModel.DataAnnotations@using Telerik.Blazor.Components.DropDownList <EditForm Model="@PageData" OnValidSubmit="@HandleValidSubmit"> <DataAnnotationsValidator /> <ValidationSummary /> @PageData.QuoteState <TelerikDropDownList bind-Value="@PageData.QuoteState" DefaultItem="@Hint" Width="300px" Data="@states" TextField="stateName" ValueField="stateID"> </TelerikDropDownList> <ValidationMessage For="@(() => PageData.QuoteState)"></ValidationMessage> <button type="submit">Submit</button> </EditForm>@functions { public MyViewModel PageData { get; set; } = new MyViewModel(); public statesModel Hint { get; set; } = new statesModel { stateID = null, stateName = "Not Selected" }; public class statesModel { public string stateID { get; set; } public string stateName { get; set; } } public class MyViewModel { [Required(ErrorMessage = "State is mandatory.")]//the value field in the dropdown model must be null in the default item public string QuoteState { get; set; } } public IEnumerable<statesModel> states = new List<statesModel> { new statesModel { stateID = "ACT", stateName = "ACT" }, new statesModel { stateID = "NSW", stateName = "NSW" }, new statesModel { stateID = "NT", stateName = "NT" }, new statesModel { stateID = "QLD", stateName = "QLD" }, new statesModel { stateID = "SA", stateName = "SA" }, new statesModel { stateID = "TAS", stateName = "TAS" }, new statesModel { stateID = "VIC", stateName = "VIC" }, new statesModel { stateID = "WA", stateName = "WA" } }; void HandleValidSubmit() { Console.WriteLine("OnValidSubmit"); }}
Posting this feature request as per your suggestion in my original forum post at: https://www.telerik.com/forums/data-source-using-scalar-list
I would like the DropDownList component to support lists of scalar values as data source. I.e:
<TelerikDropDownList Data="@MyList" bind-Value=@MyItem>
</TelerikDropDownList>
@functions {
protected List<string> MyList = new List<string>() { "a", "b", "c" };
protected string MyItem { get; set; } = "b";
}The DropDownList would infer the scalar type from the Data property. The TextField items shown in the list (and the associated ValueField) would be the same: i.e. the value of each scalar in the list.