Viewmodel 和 LINQ 查询来表示 Asp.Net MVC 中的 4 个链接表

Question

在处理将我的雇主内部系统从 asp 迁移到 asp.net MVC 之前，我使用典型的发票系统作为开发 MVC 和 ViewModel 知识的测试。

我知道 ViewModel 是在视图中显示信息的推荐方式 - 所以我希望得到一些帮助来“扁平化”以下视图模型：

表格：Invoice、InvoiceItem、Payment、PaymentInvoice

Invoice 和 InvoiceItem 已关联，Payment（记录总付款）和 PaymentInvoice（列出 Payment 涵盖的发票）也关联。

我想要一个 ViewModel 给我看：

发票编号 顾客姓名 发票总额（数量 X 单价加增值税） AmountAllocated（来自 PaymentInvoice 表） 未结（TotalofInvoice - AmountAllocated）

所以我认为我的 ViewModel 应该是：

public class InvoiceViewModel
{
    public Int InvoiceId { get; set; }
    public string CustomerName { get; set; }
    public decimal TotalofInvoice { get; set; }
    public decimal AmountAllocated { get; set; }
    public decimal Outstanding { get; set; }
}

我的领域模型是：

public class Invoice
{

    public int InvoiceId { get; set; }
    public int CustomerId { get; set; }
    public string CustomerName { get; set; }
    public string Email { get; set; }
    public DateTime InvDate { get; set; }
    public IList<InvoiceItem> InvoiceItems { get; set; }
}

public class InvoiceItem
{
    public int InvoiceItemId { get; set; }
    public int InvoiceId { get; set; }
    public string Item { get; set; }
    public string Description { get; set; }
    public int Quantity { get; set; }
    public decimal UnitPrice { get; set; }
    public decimal VAT { get; set; }
    public virtual Invoice Invoice { get; set; }

    // calculated fields
    public decimal Total
    {
        get { return Quantity * UnitPrice; }
    }
    public decimal VATAmount
    {
        get { return TotalPlusVAT - Total; }
    }
    public decimal TotalPlusVAT
    {
        get { return Total * (1 + VAT / 100); }
    }
}

public class Payment
{
    public int PaymentId { get; set; }
    public int CustomerId { get; set; }
    public DateTime DateReceived { get; set; }
    public decimal TotalReceived { get; set; }
    public IList<PaymentInvoice> PaymentInvoices { get; set; }
}

public class PaymentInvoice
{
    public int PaymentInvoiceId { get; set; }
    public int PaymentId { get; set; }
    public decimal AmountAllocated { get; set; }
    public int InvoiceId { get; set; }
    public virtual Payment Payment { get; set; }
}

我的问题是如何将 Payment 和 PaymentInvoice 表链接到 Invoice 和 InvoiceItem 表，因此我可以在我的控制器中使用 LINQ 查询来使用“扁平数据”填充视图模型。

我也迷失了 LINQ 查询 - 在 LinqPad 中我有：

from c in Invoices
join i in InvoiceItems on c.InvoiceId equals i.InvoiceId
join pi in PaymentInvoices on c.InvoiceId equals pi.InvoiceId
select new {...into ViewModel????...}

...但不知道之后该去哪里。

编辑 - 我最接近的是 Sql 来做到这一点：

SELECT     Invoices.InvoiceId, 
           Invoices.CustomerName, 
           (SUM(InvoiceItems.Quantity * InvoiceItems.UnitPrice)) AS TotalOfInvoice, 
           (SELECT     SUM(AmountAllocated) AS Expr1
                          FROM         PaymentInvoices
                          WHERE     (InvoiceId = Invoices.InvoiceId)) AS AmountAllocated, 
           SUM(InvoiceItems.Quantity * InvoiceItems.UnitPrice) 
           - (SELECT     SUM(AmountAllocated) AS Expr1
                          FROM         PaymentInvoices
                          WHERE     (InvoiceId = Invoices.InvoiceId)) AS Outstanding
FROM         Invoices LEFT OUTER JOIN
                  InvoiceItems ON Invoices.InvoiceId = InvoiceItems.InvoiceId
GROUP BY Invoices.InvoiceId, Invoices.CustomerName

谢谢，

标记

Answer 1

我认为您的 Linq 查询几乎是完美的，您只需选择新的 ViewModel：

from c in Invoices
join i in InvoiceItems on c.InvoiceId equals i.InvoiceId
join pi in PaymentInvoices on c.InvoiceId equals pi.InvoiceId
select new InvoiceViewModel {
    InvoiceId = c.InvoiceId,
    CustomerName = c.CustomerName,
    TotalofInvoice = c.InvoiceItems.Sum(invoiceitem => invoiceitem.Total(),
    AmountAllocated = ...
    Outstanding = ...
};