Сергей Горбулев

<div id="carouselExampleSlidesOnly" class="carousel slide">
    <div class="carousel-inner">
        <div class="carousel-item active">
            <div class="row no-gutters">
                <div class="col-4">
                    <img class="img-fluid" src="https://avatars.mds.yandex.net/get-pdb/401063/9d17c620-42cf-477a-bdd1-582fc34b2184/s1200?webp=false">
                </div>
                <div class="col-4">
                    <img class="img-fluid" src="https://russiaedu.ru/media/cache/image_md_resize/uploads/upload-images/2019/03/10/7oBPmO5cLho.jpg">
                </div>
                <div class="col-4">
                    <img class="img-fluid" src="https://avatars.mds.yandex.net/get-pdb/1774156/2570a25d-1f19-474e-8558-617b4c6715d9/s1200?webp=false">
                </div>
            </div>
        </div>
        <div class="carousel-item">
            <div class="row no-gutters">
                <div class="col-4">
                    <img class="img-fluid" src="https://media.metrolatam.com/2019/09/01/flores-a998dbf4fb9bd970816c45d84799ee89-1200x800.jpg">
                </div>
                <div class="col-4">
                    <img class="img-fluid" src="https://avatars.mds.yandex.net/get-pdb/2296723/d4bee5c6-d4a5-45ac-b67b-4883862bd7d5/s1200">
                </div>
                <div class="col-4">
                    <img class="img-fluid" src="https://avatars.mds.yandex.net/get-pdb/1899227/2ad11e6a-5cc9-4841-a617-37d1a948d920/s1200">
                </div>
            </div>
        </div>
    </div>
    <a class="carousel-control-prev" href="#carouselExampleSlidesOnly" role="button" data-slide="prev">
        <span class="carousel-control-prev-icon" aria-hidden="true"></span>
        <span class="sr-only">Previous</span>
    </a>
    <a class="carousel-control-next" href="#carouselExampleSlidesOnly" role="button" data-slide="next">
        <span class="carousel-control-next-icon" aria-hidden="true"></span>
        <span class="sr-only">Next</span>
    </a>
</div>

<select id='imgCombo' onChange="javascript: doIcon( this.value );" style="width: 65px;" class="icon">
<option style="background-image: url(imgselect/01.gif);" class="icon" value="01">2</option>
<option style="background-image: url(imgselect/02.gif);" class="icon" value="02">3</option>
<option style="background-image: url(imgselect/03.gif);" class="icon" value="03">4</option>
<option style="background-image: url(imgselect/04.gif);" class="icon" value="04">5</option>
<option style="background-image: url(imgselect/05.gif);" class="icon" value="05">4</option>
<option style="background-image: url(imgselect/06.gif);" class="icon" value="06">4</option>
</select>

string src=UrlHelper.GenerateContentUrl("~/Content/фотографии/фотография.jpg",this.HttpContext)

string src=Url.Content("~/Content/фотографии/фотография.jpg")

WebUserControl myControl = new WebUserControl();
       form1.Controls.Add(myControl);

WebUserControl myControl = (WebUserControl)LoadControl("~/WebUserControl.ascx");
        form1.Controls.Add(myControl);

<%@ Register Src="~/WebUserControl.ascx" TagPrefix="мойКонтрол" TagName="WebUserControl" %>