ViewModel和LINQ查詢代表Asp.Net中的4個鏈接表MVC

Question

在處理將我的僱主內部系統從asp遷移到asp.net MVC之前，我使用典型的發票系統作爲開發MVC和ViewModel知識的測試。

我知道的ViewModels是在視圖中顯示的信息的推薦方法 - 所以我希望一些幫助「扁平化」的視圖模型爲以下幾點：

表：發票，InvoiceItem，付款，PaymentInvoice

已將發票和InvoiceItem關聯起來，並且支付（記錄整體支付）和PaymentInvoice（列出哪些發票支付涵蓋）也是鏈接的。

我想一個視圖模型給我看：

InvoiceId 客戶名稱 發票（數量X單價（不含稅）） AmountAllocated（從PaymentInvoice表） 傑出（TotalofInvoice - AmountAllocated）的總

所以我覺得我的視圖模型應該是：

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; } 
} 

我的問題是如何支付和PaymentInvoice表，發票和InvoiceItem錶鏈接，這樣我就可以使用LINQ查詢在我的控制器與「扁平化數據」來填充視圖模型。

我與LINQ查詢失去了太多 - 在LinqPad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????...} 

...但不知道在哪裏後去。

編輯 - 我得到的最接近是SQL要做到這一點：

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 

謝謝

馬克

Answer 1

我覺得你的Linq查詢幾乎是完美的你只需要選擇新的ViewModels：

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 = ... 
};