The type or namespace name xxxx could not be found (are you missing a using directive or an assembly reference?)

<div dir="ltr">The type or namespace name xxxx could not be found (are you missing a using directive or an assembly reference?) <div>i searched so many websites i cant get clear answer. . provide some suggestion</div> </div> <div class="yj6qo ajU"> <div id=":8a" class="ajR" role="button" tabindex="0" data-tooltip="Show trimmed content" aria-label="Show trimmed content"></div> </div> ...