Gewusst wie: Erstellen eines Objekts mit der statischen 'Create'-Methode (Entity Framework)

Entity Framework-Tools lesen eine CSDL-Datei ein, um Code zur Definition der Objektebene zu generieren. Wenn die Datenklassen generiert werden, wird jede Klasse mit einer statischen create-Factorymethode erstellt. Diese Methode instanziiert die Objekte und legt alle Eigenschaften der Klasse fest, die nicht leer sein dürfen. Die Methode enthält einen Parameter für jede Eigenschaft, für die in der CSDL-Datei das Nullable="false"-Attribut festgelegt wurde. Verwenden Sie diese Methode, wenn Sie Objekte mit vielen erforderlichen Eigenschaften erstellen.

Die Beispiele in diesem Thema beruhen auf dem AdventureWorks Sales-Modell. Um den Code in diesem Beispiel auszuführen, müssen Sie Ihrem Projekt bereits das "AdventureWorks Sales"-Modell hinzugefügt und das Projekt für die Verwendung von Entity Framework konfiguriert haben. Verwenden Sie dazu die Verfahren aus Gewusst wie: Manuelles Konfigurieren eines Entity Framework-Projekts und Gewusst wie: Manuelles Definieren eines Entity Data Model (Entity Framework).

Beispiel

Im Folgenden finden Sie ein CSDL-Beispielfragment für den SalesOrderHeader-Typ im AdventureWorks Sales-Modell (EDM):

<EntityType Name="SalesOrderHeader">
  <Key>
    <PropertyRef Name="SalesOrderID" />
  </Key>
  <Property Name="SalesOrderID" Type="Int32" Nullable="false" />
  <Property Name="RevisionNumber" Type="Byte" Nullable="false" />
  <Property Name="OrderDate" Type="DateTime" Nullable="false" />
  <Property Name="DueDate" Type="DateTime" Nullable="false" />
  <Property Name="ShipDate" Type="DateTime" />
  <Property Name="Status" Type="Byte" Nullable="false" ConcurrencyMode="Fixed" />
  <Property Name="OnlineOrderFlag" Type="Boolean" Nullable="false" />
  <Property Name="SalesOrderNumber" Type="String" Nullable="false" MaxLength="25" Unicode="true" FixedLength="false" />
  <Property Name="PurchaseOrderNumber" Type="String" MaxLength="25" Unicode="true" FixedLength="false" />
  <Property Name="AccountNumber" Type="String" MaxLength="15" Unicode="true" FixedLength="false" />
  <Property Name="CustomerID" Type="Int32" Nullable="false" />
  <Property Name="SalesPersonID" Type="Int32" />
  <Property Name="TerritoryID" Type="Int32" />
  <Property Name="ShipMethodID" Type="Int32" Nullable="false" />
  <Property Name="CreditCardID" Type="Int32" />
  <Property Name="CreditCardApprovalCode" Type="String" MaxLength="15" Unicode="false" FixedLength="false" />
  <Property Name="CurrencyRateID" Type="Int32" />
  <Property Name="SubTotal" Type="Decimal" Nullable="false" Precision="19" Scale="4" />
  <Property Name="TaxAmt" Type="Decimal" Nullable="false" Precision="19" Scale="4" />
  <Property Name="Freight" Type="Decimal" Nullable="false" Precision="19" Scale="4" />
  <Property Name="TotalDue" Type="Decimal" Nullable="false" Precision="19" Scale="4" />
  <Property Name="Comment" Type="String" MaxLength="128" Unicode="true" FixedLength="false" />
  <Property Name="rowguid" Type="Guid" Nullable="false" />
  <Property Name="ModifiedDate" Type="DateTime" Nullable="false" />
  <NavigationProperty Name="Address" Relationship="AdventureWorksModel.FK_SalesOrderHeader_Address_BillToAddressID" FromRole="SalesOrderHeader" ToRole="Address" />
  <NavigationProperty Name="Address1" Relationship="AdventureWorksModel.FK_SalesOrderHeader_Address_ShipToAddressID" FromRole="SalesOrderHeader" ToRole="Address" />
  <NavigationProperty Name="Contact" Relationship="AdventureWorksModel.FK_SalesOrderHeader_Contact_ContactID" FromRole="SalesOrderHeader" ToRole="Contact" />
  <NavigationProperty Name="SalesOrderDetail" Relationship="AdventureWorksModel.FK_SalesOrderDetail_SalesOrderHeader_SalesOrderID" FromRole="SalesOrderHeader" ToRole="SalesOrderDetail" />
</EntityType>

Im Folgenden finden Sie ein Beispiel der statischen CreateSalesOrderHeader-Methode, die für die SalesOrderHeader-Klasse in AdventureWorks generiert wurde:

Public Shared Function CreateSalesOrderHeader(ByVal salesOrderID As Integer, _
    ByVal revisionNumber As Byte, ByVal orderDate As Date, ByVal dueDate As Date, _
    ByVal status As Byte, ByVal onlineOrderFlag As Boolean, _
    ByVal salesOrderNumber As String, ByVal customerID As Integer, _
    ByVal shipMethodID As Integer, ByVal subTotal As Decimal, ByVal taxAmt As Decimal, _
    ByVal freight As Decimal, ByVal totalDue As Decimal, ByVal rowguid As Global.System.Guid, _
    ByVal modifiedDate As Date) As SalesOrderHeader

    Dim salesOrderHeader As SalesOrderHeader = New SalesOrderHeader
    salesOrderHeader.SalesOrderID = salesOrderID
    salesOrderHeader.RevisionNumber = revisionNumber
    salesOrderHeader.OrderDate = orderDate
    salesOrderHeader.DueDate = dueDate
    salesOrderHeader.Status = status
    salesOrderHeader.OnlineOrderFlag = onlineOrderFlag
    salesOrderHeader.SalesOrderNumber = salesOrderNumber
    salesOrderHeader.CustomerID = customerID
    salesOrderHeader.ShipMethodID = shipMethodID
    salesOrderHeader.SubTotal = subTotal
    salesOrderHeader.TaxAmt = taxAmt
    salesOrderHeader.Freight = freight
    salesOrderHeader.TotalDue = totalDue
    salesOrderHeader.rowguid = rowguid
    salesOrderHeader.ModifiedDate = modifiedDate
    Return salesOrderHeader
End Function

public static SalesOrderHeader CreateSalesOrderHeader(int salesOrderID, 
    byte revisionNumber, global::System.DateTime orderDate, 
    global::System.DateTime dueDate, byte status, bool onlineOrderFlag, 
    string salesOrderNumber, int customerID, int shipMethodID, decimal subTotal, 
    decimal taxAmt, decimal freight, decimal totalDue, global::System.Guid rowguid, 
    global::System.DateTime modifiedDate)
{
    SalesOrderHeader salesOrderHeader = new SalesOrderHeader();
    salesOrderHeader.SalesOrderID = salesOrderID;
    salesOrderHeader.RevisionNumber = revisionNumber;
    salesOrderHeader.OrderDate = orderDate;
    salesOrderHeader.DueDate = dueDate;
    salesOrderHeader.Status = status;
    salesOrderHeader.OnlineOrderFlag = onlineOrderFlag;
    salesOrderHeader.SalesOrderNumber = salesOrderNumber;
    salesOrderHeader.CustomerID = customerID;
    salesOrderHeader.ShipMethodID = shipMethodID;
    salesOrderHeader.SubTotal = subTotal;
    salesOrderHeader.TaxAmt = taxAmt;
    salesOrderHeader.Freight = freight;
    salesOrderHeader.TotalDue = totalDue;
    salesOrderHeader.rowguid = rowguid;
    salesOrderHeader.ModifiedDate = modifiedDate;
    return salesOrderHeader;
}

Im Folgenden finden Sie ein Beispiel für die Verwendung der statischen CreateSalesOrderHeader-Methode für das Erstellen und Speichern eines SalesOrderHeader-Objekts:

Dim productId As Integer = 777  'Mountain-100 Black, 44
Dim quantity As Short = 1
Dim lastName As String = "Adams"
Dim firstName As String = "Frances"
Dim invoiceNumber As String = "PO123456"
Dim shipMethod As Integer = 5
Dim specialOffer As Integer = 1

Using advWorksContext As New AdventureWorksEntities()
    Try
        ' Get the Contact for the specific customer 
        ' and the related address. 
        Dim customer As Contact = advWorksContext.Contact _
        .Include("SalesOrderHeader.Address") _
        .Where("it.LastName = @lastname", _
            New ObjectParameter("lastname", lastName)) _
        .Where("it.FirstName = @firstname", _
            New ObjectParameter("firstname", firstName)) _
        .First()

        ' Get the customer's address to use to create
        ' a new order with the same address.
        Dim address As Address = customer.SalesOrderHeader _
        .First().Address()

        ' Get the Product with the requested ID.
        Dim product As Product = _
            advWorksContext.Product.Where("it.ProductID = @product_id", _
            New ObjectParameter("product_id", productId)).First()

        ' Create a new SalesOrderHeader using the static 
        ' CreateSalesOrderHeader method.
        Dim order As SalesOrderHeader = _
            SalesOrderHeader.CreateSalesOrderHeader( _
            1, Convert.ToByte(1), DateTime.Now, DateTime.Today.AddMonths(2), _
            Convert.ToByte(1), False, String.Empty, customer.ContactID, shipMethod, _
            0, 0, 0, 0, Guid.NewGuid(), DateTime.Now)

        ' Set addition order properties.
        order.Address = address
        order.Address1 = address
        order.PurchaseOrderNumber = invoiceNumber

        ' Create a new SalesOrderDetail using the static 
        ' CreateSalesOrderDetail method.
        Dim item As SalesOrderDetail = _
            SalesOrderDetail.CreateSalesOrderDetail( _
            1, 0, quantity, product.ProductID, specialOffer, product.StandardCost, _
            0, 0, Guid.NewGuid(), DateTime.Now)

        ' Add item to the items collection and 
        ' add order to the orders collection.
        order.SalesOrderDetail.Add(item)
        customer.SalesOrderHeader.Add(order)

        ' Call a custom method to recalculate totals.
        ' For more information, see "Customizing Objects."
        order.UpdateOrderTotal()

        ' Save changes pessimistically. This means that changes 
        ' must be accepted manually once the transaction succeeds.
        advWorksContext.SaveChanges()

        Console.WriteLine("Order created with order number: " _
            + order.SalesOrderNumber)
    Catch ex As Exception
        Console.WriteLine(ex.ToString())
    End Try
End Using

int productId = 777; //Mountain-100 Black, 44
short quantity = 1;
string lastName = @"Adams";
string firstName = @"Frances";
string invoiceNumber = "PO123456";
int shipMethod = 5;
int specialOffer = 1;
 
using (AdventureWorksEntities advWorksContext = 
    new AdventureWorksEntities())
{
    try
    {
        // Get the Contact for the specific customer 
        // and the related address. 
        Contact customer = advWorksContext.Contact
            .Include("SalesOrderHeader.Address")
            .Where("it.LastName = @lastname", 
                new ObjectParameter("lastname", lastName))
            .Where("it.FirstName = @firstname", 
                new ObjectParameter("firstname", firstName))
            .First();

        // Get the customer's address to use to create
        // a new order with the same address.
        Address address = customer.SalesOrderHeader
            .First().Address;

        // Get the Product with the requested ID.
        Product product = 
            advWorksContext.Product.Where("it.ProductID = @product_id",
            new ObjectParameter("product_id", productId)).First();

        // Create a new SalesOrderHeader using the static 
        // CreateSalesOrderHeader method.
        SalesOrderHeader order = SalesOrderHeader.CreateSalesOrderHeader(0,
            Convert.ToByte(1), DateTime.Now, DateTime.Today.AddMonths(2),
            Convert.ToByte(1), false, string.Empty, customer.ContactID, shipMethod, 
            0, 0, 0, 0, Guid.NewGuid(), DateTime.Now);

        // Set addition order properties.
        order.Address = address;
        order.Address1 = address;
        order.PurchaseOrderNumber = invoiceNumber;

        // Create a new SalesOrderDetail using the static 
        // CreateSalesOrderDetail method.
        SalesOrderDetail item = SalesOrderDetail.CreateSalesOrderDetail(
            1, 0, quantity, product.ProductID, specialOffer, product.StandardCost, 
            0, 0,Guid.NewGuid(), DateTime.Now);

        // Add item to the items collection and 
        // add order to the orders collection.
        order.SalesOrderDetail.Add(item);
        customer.SalesOrderHeader.Add(order);

        // Call a custom method to recalculate totals.
        // For more information, see "Customizing Objects."
        order.UpdateOrderTotal();

        // Save changes pessimistically. This means that changes 
        // must be accepted manually once the transaction succeeds.
        advWorksContext.SaveChanges();

        Console.WriteLine("Order created with order number: "
            + order.SalesOrderNumber);
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.ToString());
    }
}

Siehe auch

Konzepte

Hinzufügen, Ändern und Löschen von Objekten (Entity Framework)
Übersicht über Object Services (Entity Framework)