ObjectContext.CreateEntityKey(String, Object) Method

Reference

Definition

Namespace:: System.Data.Objects

Assembly:: System.Data.Entity.dll

Important

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Creates the entity key for a specific object, or returns the entity key if it already exists.

public:
 System::Data::EntityKey ^ CreateEntityKey(System::String ^ entitySetName, System::Object ^ entity);

public System.Data.EntityKey CreateEntityKey (string entitySetName, object entity);

member this.CreateEntityKey : string * obj -> System.Data.EntityKey

Public Function CreateEntityKey (entitySetName As String, entity As Object) As EntityKey

Parameters

entitySetName: String

The fully qualified name of the entity set to which the entity object belongs.

entity: Object

The object for which the entity key is being retrieved.

Returns

EntityKey

The EntityKey of the object.

Exceptions

ArgumentNullException

When either parameter is null.

ArgumentException

When entitySetName is empty.

-or-

When the type of the entity object does not exist in the entity set.

-or-

When the entitySetName is not fully qualified.

InvalidOperationException

When the entity key cannot be constructed successfully based on the supplied parameters.

Examples

In this example, CreateEntityKey is used to retrieve the entity key of an existing object.

private static void ApplyItemUpdates(SalesOrderDetail updatedItem)
{
    // Define an ObjectStateEntry and EntityKey for the current object.
    EntityKey key = default(EntityKey);
    object originalItem = null;

    using (AdventureWorksEntities context = new AdventureWorksEntities())
    {
        // Create the detached object's entity key.
        key = context.CreateEntityKey("SalesOrderDetails", updatedItem);

        // Get the original item based on the entity key from the context
        // or from the database.
        if (context.TryGetObjectByKey(key, out originalItem))
        {
            // Call the ApplyCurrentValues method to apply changes
            // from the updated item to the original version.
            context.ApplyCurrentValues(key.EntitySetName, updatedItem);
        }

        context.SaveChanges();
    }
}

Remarks

If an EntityKey does not exist for the entity, the CreateEntityKey method creates a new key for it.

This method is used to determine whether an object that has the same EntityKey is already attached to the ObjectContext. If an object that has the same EntityKey is already attached, an exception is raised. Use the CreateEntityKey method to try to retrieve the EntityKey of the detached object before calling the Attach method.

Applies to

Delen via