@model Guid?
@{
    string attributes = "class='form-control'";
    if (ViewBag.Disabled == true)
    {
        attributes += " disabled='disabled'";
    }
    var dataSource = new Dictionary<KeyValuePair<Guid, string>, List<EnVisage.Models.CompanyModel>>();
    if (null != (Dictionary<KeyValuePair<Guid, string>, List<EnVisage.Models.CompanyModel>>)ViewData["List"])
    {
        dataSource = (Dictionary<KeyValuePair<Guid, string>, List<EnVisage.Models.CompanyModel>>)ViewData["List"];
    }
    else
    {
        dataSource = EnVisage.Code.Utils.GetCompanies();
    }
}
<select name="@Html.DisplayNameFor(t=>t)" id="@Html.IdFor(t=>t)" @(Html.Raw(attributes))>
    @foreach (var item in dataSource)
    {
        if (!item.Value.Any())
        {
            <option value="@item.Key.Key" class="ddl-level-item">@item.Key.Value</option>
        } else
        {
            <optgroup label="@item.Key.Value">
                @foreach (var child in item.Value)
                {
                    <option value="@child.Id" class="ddl-level-item pad-left" @(child.Id.Equals(Model) ? "selected" : "")>@child.Name</option>
                }
            </optgroup>
        }
    }
</select>