Populate DropDownList using ViewData in ASP.Net Core

I have a DropDownList on my Razor page.

I am binding the DropDownList with a ViewData.

below is the code for my controller where I am getting the data from the database:

public async Task<IActionResult> Index()
{
    List<DocumentType> docTypes = new List<DocumentType>();
    docTypes = await _documentTypeService.GetDocumentTypes(deptId);

    ViewData["DocumentType"] = new SelectList(docTypes, "Id", "Description");
}  

This is how I am displaying the drop down list and I am also selecting a value for the DropDownList based on certain condition.

This is the view markup:

<table class="table table-bordered">
    <thead>
        <tr>
            <th>Type</th>
    </thead>
    <tbody>     
    @if (Model != null)
    {
        @foreach (var item in Model)
        {
            string selected = String.Empty;
              
            @foreach (var code in (SelectList)ViewData["DocumentType"])
            {
                 if (code.Text.Contains("This is the test for RCA-500"))
                 {
                       selected = code.Text;
                       break;
                 }
            }
            <tr>
                <td>
                    <select class="form-control" style="min-width:150px" id="ddldoc_@item.DocumentId" asp-items="@(new SelectList(ViewBag.DocumentType,selected))" asp-for="@item.DocumentType"></select>
                </td>
            </tr>

This drop down is displaying "Microsoft.AspNetCore.Mvc.Rendering.SelectlistItem" instead of the actual values. Not sure what am I doing wrong.

I tried removing the @ symbol from asp-items, but then I start getting a compiler error saying ";" is missing.