EntityKey Class

Definition

Namespace:

System.Data

Assembly:

System.Data.Entity.dll

Provides a durable reference to an object that is an instance of an entity type.

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)

Inheritance

Object

EntityKey

Attributes

DataContractAttribute SerializableAttribute

Implements

IEquatable<EntityKey>

Examples

These examples show you how to create and use an 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);
    }
}

Remarks

The EntityKey objects are immutable; that is, after they are constructed they cannot be modified.

For more information, see Working with Entity Keys.

Constructors

EntityKey()	Initializes a new instance of the EntityKey class.
EntityKey(String, IEnumerable<EntityKeyMember>)	Initializes a new instance of the EntityKey class with an entity set name and an IEnumerable<T> collection of EntityKeyMember objects.
EntityKey(String, IEnumerable<KeyValuePair<String,Object>>)	Initializes a new instance of the EntityKey class with an entity set name and a generic KeyValuePair collection.
EntityKey(String, String, Object)	Initializes a new instance of the EntityKey class with an entity set name and specific entity key pair.

Fields

EntityNotValidKey	A simple EntityKey identifying an entity that resulted from a failed TREAT operation.
NoEntitySetKey	A singleton EntityKey by which a read-only entity is identified.

Properties

EntityContainerName	Gets or sets the name of the entity container.
EntityKeyValues	Gets or sets the key values associated with this EntityKey.
EntitySetName	Gets or sets the name of the entity set.
IsTemporary	Gets a value that indicates whether the EntityKey is temporary.

Methods

Equals(EntityKey)	Returns a value that indicates whether this instance is equal to a specified EntityKey.
Equals(Object)	Returns a value that indicates whether this instance is equal to a specified object.
GetEntitySet(MetadataWorkspace)	Gets the entity set for this entity key from the given metadata workspace.
GetHashCode()	Serves as a hash function for the current EntityKey object. GetHashCode() is suitable for hashing algorithms and data structures such as a hash table.
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
OnDeserialized(StreamingContext)	Helper method that is used to deserialize an EntityKey.
OnDeserializing(StreamingContext)	Helper method that is used to deserialize an EntityKey.
ToString()	Returns a string that represents the current object. (Inherited from Object)

Operators

Equality(EntityKey, EntityKey)	Compares two EntityKey objects.
Inequality(EntityKey, EntityKey)	Compares two EntityKey objects.