I have two cascaded dropdownlists, in attached example car brands and selectable colors. The dependent dropdown has defaulttext option. After the parent dropdown has changed, in its event handler I reload the dependent data source and set a new valid value. If the data source does not contain the previous (!) value, the dropdownlist calls the valuechanged callback with default value. In next round when dependent dropdown holds the default value, after reloading datasource it works as expected. And parent changes again, if the updated datasource does not contain the previous dependent value the dropdownlist sets its value to default.
When I do not pass defaulttext parameter, the dependent dropdown selects the first element from the updated datasource. In my case it is not acceptable because I want to set a specific value (in this example the default color), not the first and not the default.
This feedback drives me to try setting value to default and wait for re-render the descendant dropdownlist before set the wanted value.
Is there any way to avoid this behaviour of the dropdownlist?
<TelerikDropDownList TItem="Brand"
TValue="int"
ValueField=@nameof(Brand.Id)
TextField=@nameof(Brand.Name)
Data="@BrandList"
Value="@Data.BrandId"
ValueChanged=@OnBrandChanged />
<TelerikDropDownList TItem="Color"
TValue="int"
ValueField=@nameof(Brand.Id)
TextField=@nameof(Brand.Name)
Data="@FilteredColorList"
Value="@Data.ColorId"
ValueChanged="@OnColorChanged"
DefaultText="select color ..." />async Task OnBrandChanged(int brandId)
{
Data.ColorId = default;
await Task.Delay(5);
Data.BrandId = brandId;
Data.ColorId = GetDefaultColor(brandId);
FilteredColorList = GetFilteredColorList(brandId);
}