HyperCube/Pages/Collapsible.razor

<div class="second-block__input__file__label__box" @onclick="@Toggle">
    <label class="second-block__input__file__label">
        <span>@( this.Collapsed ? "+" : "-")</span>
        <p>@LabelText</p>
    </label>    
</div>


@if (!Collapsed)
{
    <div style="margin-top: 10px">
        @ChildContent
    </div>
}

@code {
    [Parameter]
    public RenderFragment ChildContent { get; set; }
    [Parameter]
    public bool Collapsed { get; set; } = true;

    //input params coming from from page
    [Parameter]
    public string LabelText { get; set; }

    void Toggle()
    {
        Collapsed = !Collapsed;
    }
}