ASP.NET Core Razor - Post input, variable and string values

Question

I am trying to save to table three values, one coming from cshtml input

<div class="col-2">
<select class="form-control border-warning" style="font-size:12px" asp-for="PTWContent.PTWType" asp-items="Html.GetEnumSelectList<RoSafety.Models.PTW.PTWType>()">
<option value="">Permit to Work Type</option>
</select>
<span asp-validation-for="PTWContent.PTWType" class="text-danger"></span>
</div>

one from a variable and one string from cshtml.cs

var userId = User.FindFirstValue(ClaimTypes.NameIdentifier);
var addPTW = new PTWContent();
if (await TryUpdateModelAsync(addPTW, "PTWContent", s => s.PTWType, s => s.UserID == userId, s => s.WorkComplete == "No"))
{
_context.PTWContents.Add(addPTW);
await _context.SaveChangesAsync();
return RedirectToPage("./PTW");
}

The error I get is

An unhandled exception occurred while processing the request.

InvalidOperationException: The passed expression of expression node type 'Equal' is invalid. Only simple member access expressions for model properties are supported.

Microsoft.AspNetCore.Mvc.ModelBinding.ModelBindingHelper.GetPropertyName(Expression expression)