在ASP.NET MVC中传递匿名类型

Question

我在C#中使用ASP.net MVC.为什么这是代码:

public IQueryable<Product> ListProducts(string prodcutType)
{
    var results = from p in db.Products
        join s in db.Stocks
        on p.ID equals s.IDProduct
        where p.ptype == prodcutType
        select new { s.width, s.height, s.number};                 
    return results;
}

显示以下错误？

错误1无法将类型隐式转换 System.Linq.IQueryable<AnonymousType#1> 为 System.Linq.IQueryable<eim.Models.Product>.存在显式转换(您是否错过了演员？)

Answer 1

因为select new { s.width, s.height, s.number}手段System.Linq.IQueryable<AnonymousType#1>但你的功能期望返回IQueryable<Product>.将您的代码更改为:

public IQueryable<Product> ListProducts(string prodcutType)
{

    var results = from p in db.Products
                  join s in db.Stocks
                  on p.ID equals s.IDProduct
                  where p.ptype == prodcutType
                  select p;
    return results;
}

更新:

或许你想要IQueryable<Stock>:

public IQueryable<Stock> ListProducts(string prodcutType)
{

    var results = from p in db.Products
                  join s in db.Stocks
                  on p.ID equals s.IDProduct
                  where p.ptype == prodcutType
                  select s;
    return results;
}

如果只想要3个属性width + height + number,则创建新类型.例如:

public class SomeType {
    public int Width { get; set; }
    public int Height { get; set; }
    public int Number { get; set; }
}

public IQueryable<SomeType> ListProducts(string prodcutType)
{

    var results = from p in db.Products
                  join s in db.Stocks
                  on p.ID equals s.IDProduct
                  where p.ptype == prodcutType
                  select new SomeType {
                      Width = s.width,
                      Height = s.height,
                      Number = s.number
                  };
    return results;
}