Question

我有一个linq查询，它返回一个未知类型值的列表。我想在方法中包含此查询并使用该方法获取结果

public __________ getResult() {
var result = from ps in _context.PurchasingShipments
                     group ps by ps.date.Value.Year into grp
                     select new
                     {
                         Year = grp.Key,
                         Cost = grp.Sum(x => x.NoOfPieces * x.PricePerPiece + x.Micelleneous + x.TransportCost + x.SupplierCommission)
                     };

        return result;

}

上面是一个例子，getResult方法的返回类型应该是什么？请帮忙

Answer 1

解决方案1：我强烈建议您创建包含属性的模型并返回该模型的列表。

public class CostYearModel {
     public int Year { get; set; }
     public int Cost { get; set; }
}

方法如下

public List<CostYearModel> getResult() {
    var result = from ps in _context.PurchasingShipments
                 group ps by ps.date.Value.Year into grp
                 select new CostYearModel
                 {
                     Year = grp.Key,
                     Cost = grp.Sum(x => x.NoOfPieces * x.PricePerPiece + x.Micelleneous + x.TransportCost + x.SupplierCommission)
                 };

      return result.ToList();
}

解决方案2：如果您不能和/或不想为此创建模型，错误解决方案将返回对象列表。您可以使用反射来访问值。

public List<Object> getResult() {
    var result = from ps in _context.PurchasingShipments
                 group ps by ps.date.Value.Year into grp
                 select (new
                 {
                    Year = grp.Key,
                    Cost = grp.Sum(x => x.NoOfPieces * x.PricePerPiece + x.Micelleneous + x.TransportCost + x.SupplierCommission)
                 } as Object);

    return result.ToList();
}

访问每个属性的值（在您的情况下为Cost和Year）的代码如下所示。

foreach (var costYear in result)
{
    var properties = costYear.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance);
    foreach (var property in properties)
    {
        var value = property.GetValue(costYear, null);
    }
}

Answer 2

你只能返回对象，你应该创建一个类：

public class CostYearModel{
    public int Year {get; set;}
    public int Cost {get; set;}
}
public List<CostYearModel> getResult() {
    var result = from ps in _context.PurchasingShipments
                         group ps by ps.date.Value.Year into grp
                         select new CostYearModel
                         {
                             Year = grp.Key,
                             Cost = grp.Sum(x => x.NoOfPieces * x.PricePerPiece + x.Micelleneous + x.TransportCost + x.SupplierCommission)
                         };

      return result.ToList();
}

返回未知类型列表的方法

2 个答案: