c＃Razor Pages选择标签助手

Question

New to Razor, c# and ASP and with refrence to the following. https://docs.microsoft.com/en-us/aspnet/core/tutorials/razor-pages/?view=aspnetcore-2.1

Currently I'm able to arrange my rows from my model into a select view using the following code in my Pages code.

public SelectList Ratings { get; set; }

    public async Task<IActionResult> OnGetAsync()
    {

        IQueryable<string> ratingQuery = from m in _context.Ratings
                                         orderby m.MovieRating
                                         select m.MovieRating;

        Ratings = new SelectList(await ratingQuery.Distinct().ToListAsync());


        return Page();

    }

And within my HTML page reference that to produce a nice list of ratings to choose from.

<select asp-for="Movie.Rating" asp-items="Model.Ratings">
            </select>

My issue is the options generated do not have a value other than that of the Movie.Rating field (ie GOOD, BAD, UGLY), everything works ok but when I inset into the DB I would like to inset the "ID" and not the "MovieRating"

I would like to have the following html created when the page is generated. Where the ID field from within the Table is the Value and the "MovieRating" is the Text.

<select asp-for="Movie.Rating" asp-items="Model.Ratings">
  <option value="1">Good</option>
  <option value="2">Bad</option>
  <option value="3">Ugly</option>
</select> 

In order to do this I know I need to select more than the "MovieRating" field within the select statement. So I can change this to also select the ID. However it will just spit out a combined string into the option field and not produce a value field.

Is this the correct method to achieve what I want to do. I can find a few examples online of how to achieve this another way but I do not want to delve into MVC just yet.

Answer 1

Your current LINQ query is SELECT ing a single column, MovieRating and you are using the result of executing that query, which is a list of strings, to build the SelectList object. Your select tag helper is using this SelectList object which has only the MovieRating string values as the underlying items.

Assuming your Ratings class has an Id property( int type) and MovieRating property( string type), you may create a SelectListItem in the projection part of your LINQ expression.

List<SelectListItem> ratingItems = _context.Ratings
                                            .Select(a=>new SelectListItem
                                                       {
                                                          Value=a.Id.ToString(),
                                                          Text = a.MovieRating
                                                       }).ToList();

Ratings = ratingItems;
return Page();

Here the ratingItems is a list of SelectListItem objects. So change your Ratings properties type to a collection of SelectListItem objects.

public List<SelectListItem> Ratings { get; set; }