Question

非常原始的问题，但我被卡住（我猜是新手）。我有一个函数应该向我发送公司列表：另外，我希望调用者能够为下拉列表指定一个顶级元素..（比如说“无”）。我有以下代码，如何将Top Element与返回的SelectList附加？

    public static SelectList GetCompanies( bool onlyApproved, FCCIEntityDataContext entityDataContext, SelectListItem TopElement )
    {
        var cs = from c in entityDataContext.Corporates
                 where ( c.Approved == onlyApproved || onlyApproved == false )
                 select new
                 {
                     c.Id,
                     c.Company
                 };

        return new SelectList( cs.AsEnumerable(), "Id", "Comapny" );
    }

谢谢！

Answer 1

这应该适合你：

List<Corporate> corporates =
            (from c in entityDataContext.Corporates
            where (c.Approved == onlyApproved || onlyApproved == false)
            select c).ToList();
corporates.Add(new Corporate { Id = -1, Company = "None" });

return new SelectList(corporates.AsEnumerable(), "Id", "Comapny");

Answer 2

这种方法一直对我有用。

public static SelectList GetCompanies( bool onlyApproved, FCCIEntityDataContext entityDataContext, SelectListItem TopElement )
    {
            var cs = from c in entityDataContext.Corporates
                             where ( c.Approved == onlyApproved || onlyApproved == false )
                             select new SelectListItem {
                                     Value = c.Id,
                                     Text = c.Company
                             };

            var list = cs.ToList();
            list.Insert(0, TopElement);

            var selectList = new SelectList( list, "Value", "Text" );
            selectList.SelectedValue = TopElement.Value;

            return selectList;
    }

更新忘记了我在学习这些课程时学到的课程。您必须将LINQ输出为SelectListItem。

Answer 3

cs.ToList().Insert(0, new { TopElement.ID, TopElement.Company });

Answer 4

您可以将其转换为指示的列表，或者您可以将IQueryable结果与一个元素的常量数组合并（甚至对其进行排序）：

    static void Main(string[] args)
    {
        var sampleData = new[] {
            new { Id = 1, Company = "Acme", Approved = true },
            new { Id = 2, Company = "Blah", Approved = true }
        };

        bool onlyApproved = true;

        var cs = from c in sampleData
                 where (c.Approved == onlyApproved || onlyApproved == false)
                 select new
                 {
                     c.Id,
                     c.Company
                 };

        cs = cs.Union(new [] {new { Id = -1, Company = "None" }}).OrderBy(c => c.Id);

        foreach (var c in cs)
        {
            Console.WriteLine(String.Format("Id = {0}; Company = {1}", c.Id, c.Company));
        }

        Console.ReadKey();
    }

具有常数值的LINQ联盟

4 个答案: