Events

This article explains the events available in the Telerik RadioGroup for Blazor:

• OnChange
• ValueChanged
• OnBlur

The examples in this article use string values and simple data sources for brevity. You can use full models, see the data binding article for more details.

OnChange

The OnChange event represents a user action - confirmation of the current value. In inputs, it fires when the user presses Enter in the input, or when the input loses focus. In the RadioGroup, it fires when the user selects an item because there is no other action.

The OnChange event is a custom event and does not interfere with bindings, so you can use it together with models and forms.

Handle the OnChange event and use two-way binding

@SelectedValue
<br />
<TelerikRadioGroup Data="@Data" @bind-Value="@SelectedValue" OnChange="@OnChangeHandler"></TelerikRadioGroup>
@code{
    string SelectedValue { get; set; }
    IEnumerable<string> Data { get; set; } = new List<string> { "first", "second", "third" };

    async Task OnChangeHandler(object  newValue)
    {
        // the handler receives an object that you may need to cast to the type of the component
        // if you do not provide a Value, you must provide the Type parameter to the component
        Console.WriteLine($"ValueChanged fired with value: {newValue as string}");
    }
}

The event is an EventCallback. It can be synchronous and return void, or asynchronous and return async Task. Do not use async void.

ValueChanged

The ValueChanged event fires upon every change of the user selection.

The example below uses binding to primitive types for brevity, you can use full models as well.

Handle ValueChanged

@SelectedValue
<br />
<TelerikRadioGroup Data="@Data" Value="@SelectedValue" ValueChanged="@( (string v) => ValueChangedHandler(v) )"></TelerikRadioGroup>
@code{
    string SelectedValue { get; set; }
    IEnumerable<string> Data { get; set; } = new List<string> { "first", "second", "third" };

    void ValueChangedHandler(string newValue)
    {
        SelectedValue = newValue;
        //you have to update the model manually because handling the ValueChanged event does not let you use @bind-Value
        Console.WriteLine($"ValueChanged fired with value: {newValue}");
    }
}

The event is an EventCallback. It can be synchronous and return void, or asynchronous and return async Task. Do not use async void.

The lambda expression in the handler is required by the framework: https://github.com/aspnet/AspNetCore/issues/12226.

OnBlur

The OnBlur event fires when an element inside the component loses focus (radio button or the entire component).

Handle the OnBlur event

@* You may not have to use OnChange to react to loss of focus *@

<TelerikRadioGroup Data="@Data" @bind-Value="@SelectedValue"
                   OnBlur="@OnBlurHandler">
</TelerikRadioGroup>

@code{
    async Task OnBlurHandler()
    {
        Console.WriteLine($"BLUR fired, the last value WAS {SelectedValue}.");
    }

    string SelectedValue { get; set; }
    IEnumerable<string> Data { get; set; } = new List<string> { "first", "second", "third" };
}

See Also

• ValueChanged and Validation