HOW TO：使用靜態 Create 方法建立物件 (Entity Framework)
Entity Framework 工具會使用概念結構定義語言 (CSDL) 來產生可定義物件層的程式碼。 當產生資料類別時，每一個類別都是使用靜態 create Factory 方法所產生。 此方法會執行個體化物件，及設定不能為 null 之類別的所有屬性。 這個方法會針對 CSDL 中已套用 Nullable="false" 屬性 (Attribute)、模型中沒有定義預設值且可供 Entity Framework 存取的每個屬性 (Property) 包含參數。 下列範例將示範如何在概念模型中設定預設值以及屬性的 set 存取子。
<Property Name="CarrierTrackingNumber" Type="String" MaxLength="25" Unicode="true" FixedLength="false"
DefaultValue="1A-2B-3C"
a:SetterAccess="Protected" xmlns:a="https://schemas.microsoft.com/ado/2006/04/codegeneration" />
使用概念模型中的這個屬性定義，程式碼產生器將產生一個實體，其中具有預設值 "1A-2B-3C" 的 CarrierTrackingNumber 屬性以及 protected set 存取子。
在建立具有許多必要屬性的物件時，請使用這個方法。
本主題的範例根據 Adventure Works Sales Model。若要執行此主題中的程式碼，您必須已經將 Adventure Works Sales Model 加入到專案中，並設定您的專案使用 Entity Framework。如需詳細資訊，請參閱 HOW TO：使用實體資料模型精靈 (Entity Framework) 或 HOW TO：手動設定 Entity Framework 專案及 HOW TO：手動設定 Entity Framework 專案。
範例
下列是 AdventureWorks 銷售模型 中 SalesOrderDetail 型別的範例 CSDL 片段：
<EntityType Name="SalesOrderDetail">
<Key>
<PropertyRef Name="SalesOrderID" />
<PropertyRef Name="SalesOrderDetailID" />
</Key>
<Property Name="SalesOrderID" Type="Int32" Nullable="false" />
<Property Name="SalesOrderDetailID" Type="Int32" Nullable="false" annotation:StoreGeneratedPattern="Identity" />
<Property Name="CarrierTrackingNumber" Type="String" MaxLength="25" Unicode="true" FixedLength="false"
DefaultValue="1A-2B-3C"
a:SetterAccess="Protected" xmlns:a="https://schemas.microsoft.com/ado/2006/04/codegeneration" />
<Property Name="OrderQty" Type="Int16" Nullable="false" />
<Property Name="ProductID" Type="Int32" Nullable="false" />
<Property Name="SpecialOfferID" Type="Int32" Nullable="false" />
<Property Name="UnitPrice" Type="Decimal" Nullable="false" Precision="19" Scale="4" />
<Property Name="UnitPriceDiscount" Type="Decimal" Nullable="false" Precision="19" Scale="4" />
<Property Name="LineTotal" Type="Decimal" Nullable="false" Precision="38" Scale="6" annotation:StoreGeneratedPattern="Computed" />
<Property Name="rowguid" Type="Guid" Nullable="false" />
<Property Name="ModifiedDate" Type="DateTime" Nullable="false" />
<NavigationProperty Name="SalesOrderHeader" Relationship="AdventureWorksModel.FK_SalesOrderDetail_SalesOrderHeader_SalesOrderID" FromRole="SalesOrderDetail" ToRole="SalesOrderHeader" />
</EntityType>
下列是 AdventureWorks 中針對 SalesOrderDetail 類別產生之靜態 CreateSalesOrderDetail 方法的範例：
Public Shared Function CreateSalesOrderDetail(ByVal salesOrderID As Global.System.Int32, ByVal salesOrderDetailID As Global.System.Int32, ByVal orderQty As Global.System.Int16, ByVal productID As Global.System.Int32, ByVal specialOfferID As Global.System.Int32, ByVal unitPrice As Global.System.Decimal, ByVal unitPriceDiscount As Global.System.Decimal, ByVal lineTotal As Global.System.Decimal, ByVal rowguid As Global.System.Guid, ByVal modifiedDate As Global.System.DateTime) As SalesOrderDetail
Dim salesOrderDetail As SalesOrderDetail = New SalesOrderDetail
salesOrderDetail.SalesOrderID = salesOrderID
salesOrderDetail.SalesOrderDetailID = salesOrderDetailID
salesOrderDetail.OrderQty = orderQty
salesOrderDetail.ProductID = productID
salesOrderDetail.SpecialOfferID = specialOfferID
salesOrderDetail.UnitPrice = unitPrice
salesOrderDetail.UnitPriceDiscount = unitPriceDiscount
salesOrderDetail.LineTotal = lineTotal
salesOrderDetail.rowguid = rowguid
salesOrderDetail.ModifiedDate = modifiedDate
Return salesOrderDetail
End Function
public static SalesOrderDetail CreateSalesOrderDetail(global::System.Int32 salesOrderID, global::System.Int32 salesOrderDetailID, global::System.Int16 orderQty, global::System.Int32 productID, global::System.Int32 specialOfferID, global::System.Decimal unitPrice, global::System.Decimal unitPriceDiscount, global::System.Decimal lineTotal, global::System.Guid rowguid, global::System.DateTime modifiedDate)
{
SalesOrderDetail salesOrderDetail = new SalesOrderDetail();
salesOrderDetail.SalesOrderID = salesOrderID;
salesOrderDetail.SalesOrderDetailID = salesOrderDetailID;
salesOrderDetail.OrderQty = orderQty;
salesOrderDetail.ProductID = productID;
salesOrderDetail.SpecialOfferID = specialOfferID;
salesOrderDetail.UnitPrice = unitPrice;
salesOrderDetail.UnitPriceDiscount = unitPriceDiscount;
salesOrderDetail.LineTotal = lineTotal;
salesOrderDetail.rowguid = rowguid;
salesOrderDetail.ModifiedDate = modifiedDate;
return salesOrderDetail;
}
下列範例將示範如何使用靜態 CreateSalesOrderDetail 方法來建立及儲存 SalesOrderDetail 物件：
Dim orderId As Integer = 43680
Using context As New AdventureWorksEntities()
Dim order = (From o In context.SalesOrderHeaders
Where o.SalesOrderID = orderId
Select o).First()
' Add a new item.
Dim newItem As SalesOrderDetail = SalesOrderDetail.CreateSalesOrderDetail(0, 0, 5, 711, 1, CDec(13.0368), _
0, 0, Guid.NewGuid(), DateTime.Now)
order.SalesOrderDetails.Add(newItem)
context.SaveChanges()
End Using
int orderId = 43680;
using (AdventureWorksEntities context
= new AdventureWorksEntities())
{
var order = (from o in context.SalesOrderHeaders
where o.SalesOrderID == orderId
select o).First();
// Add a new item.
SalesOrderDetail newItem = SalesOrderDetail.CreateSalesOrderDetail(
0, 0, 5, 711, 1, (decimal)13.0368,
0, 0, Guid.NewGuid(), DateTime.Now);
order.SalesOrderDetails.Add(newItem);
context.SaveChanges();
}