Events

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

• OnChange
• ValueChanged
• OnBlur

OnChange

The OnChange event represents a user action - confirmation of the current value. It fires when the user presses Enter in the input, or when the input loses focus.

The date input is a generic component, so you must provide either a Value, or a type to the T parameter of the component.

Handle OnChange

@result
<br />

<TelerikDateInput T="DateTime" OnChange="@MyOnChangeHandler"></TelerikDateInput>

@code {
    string result;

    private void MyOnChangeHandler(object theUserInput)
    {
        // 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
        result = string.Format("The user entered: {0:dd/MMM/yyyy}", (DateTime)theUserInput);
    }
}

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

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

Handle OnChange and use two-way binding

@result
<br />
model value: @theInputValue
<br />

<TelerikDateInput @bind-Value="@theInputValue" OnChange="@MyOnChangeHandler"></TelerikDateInput>

@code {
    string result;

    DateTime? theInputValue { get; set; } = DateTime.Now;

    private void MyOnChangeHandler(object theUserInput)
    {
        // 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
        result = string.Format("The user entered: {0:dd/MMM/yyyy}", (theUserInput as DateTime?).Value);
    }
}

ValueChanged

The ValueChanged event fires upon every change (for example, keystroke) in the input.

Handle ValueChanged

@result
<br />

<TelerikDateInput ValueChanged="@( (DateTime d) => MyValueChangeHandler(d) )"></TelerikDateInput>

@code {
    string result;

    private void MyValueChangeHandler(DateTime theUserInput)
    {
        result = string.Format("The user entered: {0}", theUserInput);
    }
}

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.

Handle ValueChanged and provide initial value

@result
<br />
model value: @theInputValue
<br />

<TelerikDateInput Value="@theInputValue" ValueChanged="@( (DateTime d) => MyValueChangeHandler(d) )"></TelerikDateInput>

@code {
    string result;

    DateTime theInputValue { get; set; } = DateTime.Now;

    private void MyValueChangeHandler(DateTime theUserInput)
    {
        result = string.Format("The user entered: {0:dd/MMM/yyyy}", theUserInput);

        //you have to update the model manually because handling the ValueChanged event does not let you use @bind-Value
        theInputValue = theUserInput;
    }
}

OnBlur

The OnBlur event fires when the component loses focus.

Handle the OnBlur event

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

<TelerikDateInput @bind-Value="@TheDate"
                  OnBlur="@OnBlurHandler">
</TelerikDateInput>

@code{
    async Task OnBlurHandler()
    {
        Console.WriteLine($"BLUR fired, current value is {TheDate}.");
    }

    DateTime? TheDate { get; set; } = DateTime.Now;
}

See Also

• ValueChanged and Validation
• Fire OnChange Only Once