DbContext.set() cannot create a DbSet for entity because this type is not included in the model for the context

I'm using zzz-5 zzz. I useDbContext.Set() yet, I'm getting the problem "Cannot build a DbSet for 'MediaDate' since this type is not included in the model for the context."

Here's my code:

var context = new GoldentaurusContext();
DbSet<MediaDate> set = context.Set<MediaDate>();
mediaDateList = set.FromSql("[dbo].[sp_GetMediaDate]")
                .Select(x => new SelectListItem { Text = x.DateText, Value = x.DateValue })
                .ToList();

The class MediaDate:

public class MediaDate
{
    public string DateText { get; set; }
    public string DateValue { get; set; }
}

Why is the MediaDate class needed in addition to the DbContext class?

Please tell me what I'm doing incorrectly.