EntityKey Classe

Definizione

public ref class EntityKey sealed : IEquatable<System::Data::EntityKey ^>

[System.Runtime.Serialization.DataContract(IsReference=true)]
[System.Serializable]
public sealed class EntityKey : IEquatable<System.Data.EntityKey>

[<System.Runtime.Serialization.DataContract(IsReference=true)>]
[<System.Serializable>]
type EntityKey = class
    interface IEquatable<EntityKey>

Public NotInheritable Class EntityKey
Implements IEquatable(Of EntityKey)

Ereditarietà

Object

EntityKey

Attributi

DataContractAttribute SerializableAttribute

Implementazioni

IEquatable<EntityKey>

Esempio

Questi esempi illustrano come creare e usare un oggetto EntityKey.

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    Object entity = null;
    IEnumerable<KeyValuePair<string, object>> entityKeyValues =
        new KeyValuePair<string, object>[] {
            new KeyValuePair<string, object>("SalesOrderID", 43680) };

    // Create the  key for a specific SalesOrderHeader object.
    EntityKey key = new EntityKey("AdventureWorksEntities.SalesOrderHeaders", entityKeyValues);

    // Get the object from the context or the persisted store by its key.
    if (context.TryGetObjectByKey(key, out entity))
    {
        Console.WriteLine("The requested " + entity.GetType().FullName +
            " object was found");
    }
    else
    {
        Console.WriteLine("An object with this key " +
            "could not be found.");
    }
}

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    try
    {
        // Create the key that represents the order.
        EntityKey orderKey =
            new EntityKey("AdventureWorksEntities.SalesOrderHeaders",
                "SalesOrderID", orderId);

        // Create the stand-in SalesOrderHeader object
        // based on the specified SalesOrderID.
        SalesOrderHeader order = new SalesOrderHeader();
        order.EntityKey = orderKey;

        // Assign the ID to the SalesOrderID property to matche the key.
        order.SalesOrderID = (int)orderKey.EntityKeyValues[0].Value;

        // Attach the stand-in SalesOrderHeader object.
        context.SalesOrderHeaders.Attach(order);

        // Create a new SalesOrderDetail object.
        // You can use the static CreateObjectName method (the Entity Framework
        // adds this method to the generated entity types) instead of the new operator:
        // SalesOrderDetail.CreateSalesOrderDetail(1, 0, 2, 750, 1, (decimal)2171.2942, 0, 0,
        //                                         Guid.NewGuid(), DateTime.Today));
        SalesOrderDetail detail = new SalesOrderDetail
        {
            SalesOrderID = orderId,
            SalesOrderDetailID = 0,
            OrderQty = 2,
            ProductID = 750,
            SpecialOfferID = 1,
            UnitPrice = (decimal)2171.2942,
            UnitPriceDiscount = 0,
            LineTotal = 0,
            rowguid = Guid.NewGuid(),
            ModifiedDate = DateTime.Now
        };

        order.SalesOrderDetails.Add(detail);

        context.SaveChanges();
    }
    catch (InvalidOperationException)
    {
        Console.WriteLine("Ensure that the key value matches the value of the object's ID property.");
    }
    catch (UpdateException)
    {
        Console.WriteLine("An error has occurred. Ensure that an object with the '{0}' key value exists.",
        orderId);
    }
}

Commenti

Gli oggetti EntityKey non sono modificabili, ossia non possono essere modificati dopo essere stati costruiti.

Per altre informazioni, vedere Uso delle chiavi di entità.

Costruttori

Campi

Proprietà

Metodi

Operatori

Si applica a