Question

我正在尝试使用包含嵌套类数组的LINQ填充实例。我已设法使用以下LINQ执行此操作。我还在select中包含了构成实例的类。

    select new EditableWarrantBook {
        Id = p1.id,
        Comment = p1.EntryComment,
        WarrantYear1 = new BookYear {
            StatusYear = p2.StatusYear,
            Status = p2.Status,
        },
        WarrantYear2 = new BookYear {
            StatusYear = p3.StatusYear,
            Status = p3.Status,
        },
        WarrantYear3 = new BookYear {
            StatusYear = p4.StatusYear,
            Status = p4.Status,
        }
    }

public class EditableWarrantBook
{
    public int Id { get; set; }
    public string Comment { get; set; }

    public BookYear[] WarrantYear = new BookYear[3];

    public BookYear WarrantYear1
    {
        get { return WarrantYear[0]; }
        set { WarrantYear[0] = value; }
    }
    public BookYear WarrantYear2
    {
        get { return WarrantYear[1]; }
        set { WarrantYear[1] = value; }
    }
    public BookYear WarrantYear3
    {
        get { return WarrantYear[2]; }
        set { WarrantYear[2] = value; }
    }

}

public class BookYear
{
    public int? StatusYear { get; set; } 
    public string Status { get; set; } 
}

这有效我可以使用WarrantYear[0]或WarrantYear1访问值。在设计UI时，这有时很有用。但是，在这种情况下，我不需要WarrantYear1属性，因为我将其转换为JSON并且我不需要重复（或者想要在网络上发送相同数据的两个版本）。我的问题是，如何编写select语句来加载WarrantYear数组。或者我如何编写类，以便我可以作为属性访问该数组。我的解决方案不应包含Warrant1, Warrant2, Warrant3类中的EditableWarrantBook属性。

Answer 1

由于我无法在没有Warrant1，Warrant2和Warrant3属性的情况下让select工作，我将其原样保留并重写该类，以便JSON序列化程序创建一个没有Warrant1，Warrant2和Warrant3属性的JSON实例。我使用this文章的反思。为了澄清这个问题，我的第一次尝试是创建一个JSON有效负载，它的大小是原来的两倍，因为JSON序列化器同时创建了Warrant1，Warrant2和Warrant3结构以及Warrant []数组。使用JSON结果的基类重写类，只有Warrant []数组满足Webservice的接口要求。

namespace my.Models
{
public class WarrantBook
{
    public int Id { get; set; } 
    public string Comment { get; set; }

    BookYear[] warrantYear = new BookYear[3];

    public BookYear[] WarrantYear
    {
        get { return warrantYear; }
        set { warrantYear = value; }
    }
}

public class EditableWarrantBook : WarrantBook  
{
    public BookYear WarrantYear1
    {
        get { return WarrantYear[0]; }
        set { WarrantYear[0] = value; }
    }
    public BookYear WarrantYear2
    {
        get { return WarrantYear[1]; }
        set { WarrantYear[1] = value; }
    }
    public BookYear WarrantYear3
    {
        get { return WarrantYear[2]; }
        set { WarrantYear[2] = value; }
    }

}
public class BookYear
{
    public int? StatusYear { get; set; } 
    public string Status { get; set; } 
}

public static class Ext
{
    public static void CopyProperties(this EditableWarrantBook  source, WarrantBook destination)
    {
        // Iterate the Properties of the destination instance and   
        // populate them from their source counterparts   
        PropertyInfo[] destinationProperties = destination.GetType().GetProperties();
        foreach (PropertyInfo destinationPi in destinationProperties)
        {
            PropertyInfo sourcePi = source.GetType().GetProperty(destinationPi.Name);
            destinationPi.SetValue(destination, sourcePi.GetValue(source, null), null);
        }
    }
}

}

用法WCF REST Web服务

        [WebGet(UriTemplate = "GetWarrant?id={s}&user={user}")]
    public WarrantBook GetWarrant(string s, string user)
    {
        int id;
        if (int.TryParse(s, out id))
        {
            EditableWarrantBook model = SessionWarrantBook.One(p => p.Id == id);
            model.CheckedOutBy = user; // need to add checkout code
            WarrantBook jsonModel = new WarrantBook();
            model.CopyProperties(jsonModel);
            return jsonModel;
        }
        return new WarrantBook();
    }

Answer 2

问题在于您尝试将SQL世界（构建查询）与CLR世界（创建新对象）混合在一起。解决这个问题的方法是将查询分解为初始数据获取查询（SQL世界），然后枚举结果以转换为对象（CLR世界）：

所以在where p1.SaleYear == 2009之后，添加：

select new { p1, p2, p3, p4 })
.AsEnumerable()
.Select(tr => new EditableWarrantBook
    {
    Id = tr.p1.id,
    Comment = tr.p1.EntryComment,
    WarrantYear = new[] {
        tr.p2 == null ? (BookYear)null : new BookYear // EDITED LINE
        {
            StatusYear = tr.p2.StatusYear,
            Status = tr.p2.Status,
        },
        tr.p3 == null ? (BookYear)null : new BookYear // EDITED LINE
        {
            StatusYear = tr.p3.StatusYear,
            Status = tr.p3.Status,
        },
        tr.p4 == null ? (BookYear)null : new BookYear // EDITED LINE
        {
            StatusYear = tr.p4.StatusYear,
            Status = tr.p4.Status,
        }}
    }).ToList();

如果您想保留查询语法，只需将其更改为：

result = from tr in 
    (/*Select up to the AsEnumerable call above)*/).AsEnumerable()
    select new EditableWarrantBook
        {
            /* Initialization code supplied above */
        }

编辑：所以我再次修改了这个例子。它看起来像你要回来的值之一是null，所以我添加了一个空检查以确保你没有访问空对象的属性（虽然我没有检查p1是否为null ）。

Linq Select中的嵌套数组

2 个答案: