ASP.NET将IQueryable转换为List

grinderke 发表于 Dev

格林德克

我有以下错误的以下代码：

错误1无法将类型隐式转换'System.Linq.IQueryable<Receptura_v4.Models.ReceptDTO>'为'Receptura_v4.Models.ReceptDTO'。存在显式转换（您是否缺少演员表？）

有什么想法如何解决吗？

public ReceptDTO GetReceptForUser(string userId)
{
    using (ApplicationDbContext db = new ApplicationDbContext())
    { 
        var q = from r in db.Recipes where r.UserId == userId select new ReceptDTO
            {
                 RecipeID = r.RecipeID,
                 Title = r.Title,
                 Portion = r.Portion,
                 Time = r.Time,
                 Category = r.Category,
                 Preparation = r.Preparation,
                 Difficulty = r.Difficulty,
                 Views = 0,
                 Price = r.Price,
                 Date = DateTime.Now,
                 UserId = userId
            };
        return q;
    }
}

Praveen Paulose

该错误表示您的退货类型与您要退回的商品不匹配。您的返回类型为，ReceptDTO而您正在返回的类型为IQueryable<ReceptDTO>

您可以ReceptDTO通过从IQueryable

public ReceptDTO GetReceptForUser(string userId)
{
    using (ApplicationDbContext db = new ApplicationDbContext())
    { 
        var q = from r in db.Recipes where r.UserId == userId select new ReceptDTO
            {
                 RecipeID = r.RecipeID,
                 Title = r.Title,
                 Portion = r.Portion,
                 Time = r.Time,
                 Category = r.Category,
                 Preparation = r.Preparation,
                 Difficulty = r.Difficulty,
                 Views = 0,
                 Price = r.Price,
                 Date = DateTime.Now,
                 UserId = userId
            };
        return q.FirstOrDefault();
    }
}

如果需要返回列表，则可以更改方法的返回类型并返回ReceptDTO的列表

public List<ReceptDTO> GetReceptForUser(string userId)
{
    using (ApplicationDbContext db = new ApplicationDbContext())
    { 
        var q = from r in db.Recipes where r.UserId == userId select new ReceptDTO
            {
                 RecipeID = r.RecipeID,
                 Title = r.Title,
                 Portion = r.Portion,
                 Time = r.Time,
                 Category = r.Category,
                 Preparation = r.Preparation,
                 Difficulty = r.Difficulty,
                 Views = 0,
                 Price = r.Price,
                 Date = DateTime.Now,
                 UserId = userId
            };
        return q.ToList();
    }
}