Blazor Collapse

Toggle the visibility of content across your project with the Blazor Bootstrap Collapse component.

Parameters

Name	Type	Default	Required	Description	Added Version
ChildContent	RenderFragment	null	✔️	Specifies the content to be rendered inside the collapse.	1.7.0
Horizontal	bool	false		Gets or sets the horizontal.	1.7.0
Parent	string	null		Gets or sets the parent.	1.7.0
Toggle	bool	false		Toggles the collapsible element on invocation.	1.7.0

Methods

Name	Description	Added Version
ShowAsync	Shows a collapsible element.	1.7.0
HideAsync	Hides a collapsible element.	1.7.0
ToggleAsync	Toggles a collapsible element to shown or hidden.	1.7.0

Events

Name	Description	Added Version
OnShowing	This event fires immediately when the show instance method is called.	1.7.0
OnShown	This event is fired when a collapse element has been made visible to the user (will wait for CSS transitions to complete).	1.7.0
OnHiding	This event is fired immediately when the hide method has been called.	1.7.0
OnHidden	This event is fired when a collapse element has been hidden from the user (will wait for CSS transitions to complete).	1.7.0

How it works

The Collapse component is used to show and hide content. Use ShowAsync, HideAsync, and ToggleAsync methods to toggle the content. Collapsing an element will animate the height from its current value to 0.

info

The animation effect of this component is dependent on the prefers-reduced-motion media query. See the reduced motion section of our accessibility documentation.

Examples

Click the buttons below to show and hide the content.

<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="ShowContentAsync">Show content</Button>
<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="HideContentAsync">Hide content</Button>
<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="ToggleContentAsync">Toggle content</Button>

<Collapse @ref="collapse1">
    <Card>
        <CardBody>
            Some placeholder content for the collapse component. This panel is hidden by default but revealed when the user activates the relevant trigger.
        </CardBody>
    </Card>
</Collapse>

@code {
    Collapse collapse1 = default!;

    private async Task ShowContentAsync() => await collapse1.ShowAsync();
    private async Task HideContentAsync() => await collapse1.HideAsync();
    private async Task ToggleContentAsync() => await collapse1.ToggleAsync();
}

See demo here

Horizontal

The Collapse component supports horizontal collapsing. Set the Horizontal parameter to true to enable horizontal collapsing.

<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="ShowContentAsync">Show content</Button>
<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="HideContentAsync">Hide content</Button>
<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="ToggleContentAsync">Toggle content</Button>

<Collapse @ref="collapse1" Horizontal="true">
    <Card Style="width:300px;">
        <CardBody>
            This is some placeholder content for a horizontal collapse. It's hidden by default and shown when triggered.
        </CardBody>
    </Card>
</Collapse>

@code {
    Collapse collapse1 = default!;

    private async Task ShowContentAsync() => await collapse1.ShowAsync();
    private async Task HideContentAsync() => await collapse1.HideAsync();
    private async Task ToggleContentAsync() => await collapse1.ToggleAsync();
}

See demo here

Events Example

Blazor Bootstrap Collapse component exposes a few events for hooking into collapse functionality.

<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="ShowContentAsync">Show content</Button>
<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="HideContentAsync">Hide content</Button>
<Button Type="ButtonType.Button" Color="ButtonColor.Primary" @onclick="ToggleContentAsync">Toggle content</Button>
<Button Type="ButtonType.Button" Color="ButtonColor.Secondary" @onclick="ClearMessage">Clear Messages</Button>

<Collapse @ref="collapse1"
          Class="mt-3"
          OnShowing="OnCollapseShowingAsync"
          OnShown="OnCollapseShownAsync"
          OnHiding="OnCollapseHidingAsync"
          OnHidden="OnCollapseHiddenAsync">
    <Card>
        <CardBody>
            Some placeholder content for the collapse component. This panel is hidden by default but revealed when the user activates the relevant trigger.
        </CardBody>
    </Card>
</Collapse>

<div class="mt-3">
    @foreach (var item in messages)
    {
        <p>@item</p>
    }
</div>

@code {
    Collapse collapse1 = default!;

    List<string> messages = new List<string>();

    private async Task ShowContentAsync() => await collapse1.ShowAsync();
    private async Task HideContentAsync() => await collapse1.HideAsync();
    private async Task ToggleContentAsync() => await collapse1.ToggleAsync();

    private void OnCollapseShowingAsync() => messages.Add($"Event: OnShowing called {DateTime.Now.ToLocalTime()}");

    private void OnCollapseShownAsync() => messages.Add($"Event: OnShown called {DateTime.Now.ToLocalTime()}");

    private void OnCollapseHidingAsync() => messages.Add($"Event: OnHiding called {DateTime.Now.ToLocalTime()}");

    private void OnCollapseHiddenAsync() => messages.Add($"Event: OnHidden called {DateTime.Now.ToLocalTime()}");

    private void ClearMessage() => messages = new List<string>();
}