Currently, a TextField value of empty string will produce a blank item in the dropdown.
On the other hand, a null TextField value will produce the fully qualified class name.
Here are possible workarounds: https://blazorrepl.telerik.com/myOlFpFb1465jW8E07
At the moment, typing with the keyboard focuses the first item that starts with the last letter you pressed. To focus the next one you should either use Down Arrow, or type the same letter again.
I would like it to behave like the regular <select> or like a combo box with filtering - typing characters quickly should highlight the item that begins with all those characters, instead of using only the first letter.
===
Admit edit: some keywords for better findability: DropDownList keyboard search filter accessibility
The DropDownList component is too basic to be used in complex environments. In the real world, no one is binding DropDownLists to List<string>, they are binding to complex datatypes, and the ability to do so has been present in MVC apps for a long time.
Given the following code, it is possible to bind to a List<object>, and two-way bind to the object that was selected.
<select @onchange="@OnChangedAsync">
<option></option>
@if (DataSource != null)
{
@foreach (var item in DataSource)
{
<option @key="item" value="@optionValueFunc(item)" selected="@(item.Equals(SelectedItem))">@optionTextFunc(item)</option>
}
}
</select>
#region Private Members
private Func<TSource, object> optionTextFunc;
private Func<TSource, object> optionValueFunc;
private TSource selectedItem = default(TSource);
#endregion
#region Public Parameters
/// <summary>
/// A List of objects to bind against.
/// </summary>
[Parameter]
public IList<TSource> DataSource { get; set; } = new List<TSource>();
/// <summary>
/// A lambda expression referencing the property containing the text to display to the end user. Example: @(c => c.DisplayName)
/// </summary>
[Parameter]
public Expression<Func<TSource, object>> OptionText { get; set; }
/// <summary>
/// A lambda expression referencing the property containing the value for this object, usually an identifier. Example: @(c => c.Id)
/// </summary>
[Parameter]
public Expression<Func<TSource, object>> OptionValue { get; set; }
/// <summary>
/// The item from the <see cref="DataSource" /> that has been selected.
/// </summary>
[Parameter]
public TSource SelectedItem { get; set; }
/// <summary>
/// The callback event required for two-way binding.
/// </summary>
[Parameter]
public EventCallback<TSource> SelectedItemChanged { get; set; }
#endregion
private async Task OnChangedAsync(ChangeEventArgs changeEventArgs)
{
await UpdateSelection(DataSource.FirstOrDefault(c => optionValueFunc(c).ToString() == changeEventArgs.Value.ToString()));
}
private async Task UpdateSelection(TSource item)
{
selectedItem = item;
await SelectedItemChanged.InvokeAsync(selectedItem);
}
protected override async Task OnInitializedAsync()
{
if (optionTextFunc == null && OptionText != null)
{
optionTextFunc = OptionText.Compile();
}
if (optionValueFunc == null && OptionText != null)
{
optionValueFunc = OptionValue.Compile();
}
await Task.CompletedTask;
}
Would really appreciate it if you would consider adding this to the next release.
Hi,
Is it possible to implement search/look-ahead in the current version of the DropDown component? If not, will you be adding this feature soon?
Thank you.
Ben
I need to be able to allow our users to tab into the dropdownlist control and open it with enter (similar to standard HTML select).
Here is also a sample from the W3 documentation to compare against: DropDownList keyboard support.
Right now when a DropDownList has PopupHeight="Auto" the popup gets the height necesaary to display its items properly.
But when there are many items the popup also displays all items without a vertical scrollbar (maybe over the entire page and beyond), which is not good.
My suggestion would be to add a property for specifyig a "MaxPopupHeight" to limit the growth of the popup.
Also if "PopupHeight" is not specified it should take "Auto" as the default value instead of a static height in px, instead give the new "MaxPopupHeight" a limiting default value.
***Admin Edit***
Released in 3.0.0 through PopupSettings tag: https://docs.telerik.com/blazor-ui/upgrade/breaking-changes/3-0-0#popup-settings
***Admin Edit***
This will allow the dropdown to be large enough to fit a reasonable number of items without a scrollbar. Alternatively, you could limit it through a pixel value you can set, or through the MaxPopupHeight property if it gets implemented: https://feedback.telerik.com/blazor/1412653-maxpopupheight.
Hello everyone,
We have opened this Feature Request to gather your insights on the addition of disabled items for the DropDownList.
For the time being, you can make items look disabled via DropDownListItemTemplate. Also, prevent clicks with @onclick and use the ValueChanged event to skip disabled items during keyboard navigation.
UPDATE: The associated built-in feature is the OnItemRender event, which can help style specific items without a template.
<TelerikDropDownList Data="@Products"
TItem="@Product"
TValue="@(int?)"
Value="@SelectedProductId"
ValueField="@nameof(Product.Id)"
TextField="@nameof(Product.Name)"
DefaultText="Select Product..."
ValueChanged="@( (int? newValue) => SelectedProductChanged(newValue) )"
Width="200px">
<DropDownListSettings>
<DropDownListPopupSettings Class="disabled-items" />
</DropDownListSettings>
<ItemTemplate>
@{ var p = context as Product; }
<div class="item-div @( !p.Active ? "disabled" : "" )"
@onclick:preventDefault="@(!p.Active)"
@onclick:stopPropagation="@(!p.Active)">
@p.Name
</div>
</ItemTemplate>
</TelerikDropDownList>
<style>
/* remove default item padding to prevent selection outside the template div */
.disabled-items .k-list-item {
padding: 0;
}
/* add back inner padding */
.disabled-items .item-div {
padding: 4px 8px;
}
/* style disabled items */
.disabled-items .disabled {
cursor: not-allowed;
width: 100%;
color: #ccc;
}
</style>
@code {
private List<Product> Products { get; set; }
private int? SelectedProductId { get; set; }
private async Task SelectedProductChanged(int? newValue)
{
var newProduct = Products.FirstOrDefault(x => x.Id == newValue);
if (newProduct?.Active == true || !newValue.HasValue)
{
// select only active items or DefaultText
SelectedProductId = newValue;
}
else
{
// skip disabled items during keyboard navigation
var oldProductIndex = Products.FindIndex(x => x.Id == SelectedProductId);
var newProductIndex = Products.FindIndex(x => x.Id == newValue);
if (newProductIndex > oldProductIndex)
{
// skip forward
SelectedProductId = Products[++newProductIndex].Id;
}
else
{
// skip backward
SelectedProductId = Products[--newProductIndex].Id;
}
}
}
protected override void OnInitialized()
{
Products = new List<Product>();
for (int i = 1; i <= 7; i++)
{
var active = i % 3 != 0;
Products.Add(new Product()
{
Id = i,
Name = (active ? "" : "Disabled ") + "Product " + i,
Active = active
});
}
base.OnInitialized();
}
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public bool Active { get; set; }
}
}
Is it possible to drop dropDownList from outside, for example after its data has been changed, without clicking on it ?
ADMIN EDIT:
This feature is also applicable to ComboBox, AutoComplete, Multiselect, Date and Time Pickers components.
Hello,
would it be possible to add "OnFocus" event to DropDownList as there is already "OnBlur" event?
Thanks
As stated in the documentation the Event OnChange for DropDownList is shown by intellisense but should not be used. However, in some situations it would be very useful to bind the value of the DropDownList and additionally have an event when the value changes, e.g. show additional inputs when a value is selected.
Currently it is either possible to have data binding to value by @bind-Value or listen for the changed event by using Value and ValueChanged.
Add the ability to make the drop down list expanded contents wider than the closed control, or just automatically determine appropriate width (doesn't always work well for very long text fields, so you need both properties).