Welcome To Blazor!

            ------------------------------------------Pages\Upravlen_HTML\MainComponent.razor
            @page "/MainComponent"
            <p><h4>Пример. <a target="_blank" href="https://docs.microsoft.com/ru-ru/aspnet/core/blazor/components/?view=aspnetcore-5.0#conditional-html-element-attributes"> Условные атрибуты элемента HTML. Управление элментами HTML.</a></h4></p>

            <hr />

            <p> <HeadingComponent /></p>

 
            -------------------------------------Pages\Upravlen_HTML\HeadingComponent.razor
@using System.Globalization


<div style="margin-top:15px;
        padding:10px;
        width:35%;
        border: 1px solid gray">

    <h1 style="font-style:@headingFontStyle">@headingText</h1>
    
    <form>
        <div>
            <label class="form-check-label">
                <input type="checkbox" id="italicsCheck"
                       @bind="italicsCheck" />
                Use italics
            </label>
        </div>

        <button type="button" class="btn btn-primary" @onclick="UpdateHeading">
            Update heading
        </button>
    </form>
</div>

    @code {
        private static TextInfo tinfo = CultureInfo.CurrentCulture.TextInfo;
        private string headingText = tinfo.ToTitleCase("welcome to blazor!");
           
        private string headingFontStyle = "normal";
        private bool italicsCheck = false;

        public void UpdateHeading()
        {
            headingFontStyle = italicsCheck ? "italic" : "normal";
        }
    }