ExpansionPanel Events

Updated on Jul 16, 2026

This article describes the available events in the Telerik ExpansionPanel for Blazor.

ExpandedChanged

The ExpansionPanel ExpandedChanged event fires when:

• The user expands or collapses the component.
• The app executes the component's ExpandAsync, CollapseAsync, or ToggleAsync method.

Make sure to update the value of the Expanded parameter by using the boolean argument that the event handler receives.

Using the ExpansionPanel events

<p>Last Event: @ExpansionPanelEventLog</p>

<p><TelerikButton OnClick="@OnToggleButtonClick">Toggle</TelerikButton></p>

<TelerikExpansionPanel @ref="ExpansionPanelRef"
                       Expanded="@ExpansionPanelExpanded"
                       ExpandedChanged="@ExpansionPanelExpandedChanged"
                       Title="Expansion Panel Title">
    <Content>
        ExpansionPanel Content
    </Content>
</TelerikExpansionPanel>

@code {
    private TelerikExpansionPanel? ExpansionPanelRef;

    private bool ExpansionPanelExpanded { get; set; }

    private string ExpansionPanelEventLog { get; set; } = string.Empty;

    private void ExpansionPanelExpandedChanged(bool newExpanded)
    {
        ExpansionPanelExpanded = newExpanded;
        ExpansionPanelEventLog = $"ExpansionPanel ExpandedChanged event fired with new value: {newExpanded}";
    }

    private async Task OnToggleButtonClick()
    {
        await ExpansionPanelRef!.ToggleAsync();
    }
}

See Also

• ExpansionPanel API Reference