Try your search with a different keyword or use * as a wildcard.
@model List<int>
@{
var htmlAttributes = ViewData["htmlAttributes"] as Dictionary<string, object> ?? new();
htmlAttributes.TryAdd("class", "form-control select2");
htmlAttributes.TryAdd("style", "width: 100%;");
htmlAttributes.TryAdd("data-dropdown-css-class", "select2-blue");
htmlAttributes.TryAdd("multiple", "multiple");
}
<div class="select2-blue">
@Html.ListBox("", ViewData["SelectList"] as IEnumerable<SelectListItem>, htmlAttributes)
</div>
<script>
$(function() {
$("#@Html.IdForModel()").select2();
});
</script>