ObjectStateManager.TryGetObjectStateEntry Metodo

Definizione

Tenta di restituire un oggetto ObjectStateEntry per una voce di oggetto o di relazione specifica.Tries to return an ObjectStateEntry object for a specific object or relationship entry.

Overload

TryGetObjectStateEntry(EntityKey, ObjectStateEntry)

Tenta di recuperare l'oggetto ObjectStateEntry corrispondente per l'oggetto o la relazione con l'oggetto EntityKey specificato.Tries to retrieve the corresponding ObjectStateEntry for the object or relationship with the specified EntityKey.

TryGetObjectStateEntry(Object, ObjectStateEntry)

Tenta di recuperare l'oggetto ObjectStateEntry corrispondente per l'oggetto Object specificato.Tries to retrieve the corresponding ObjectStateEntry for the specified Object.

TryGetObjectStateEntry(EntityKey, ObjectStateEntry)

Tenta di recuperare l'oggetto ObjectStateEntry corrispondente per l'oggetto o la relazione con l'oggetto EntityKey specificato.Tries to retrieve the corresponding ObjectStateEntry for the object or relationship with the specified EntityKey.

public:
 bool TryGetObjectStateEntry(System::Data::EntityKey ^ key, [Runtime::InteropServices::Out] System::Data::Objects::ObjectStateEntry ^ % entry);
public bool TryGetObjectStateEntry (System.Data.EntityKey key, out System.Data.Objects.ObjectStateEntry entry);
member this.TryGetObjectStateEntry : System.Data.EntityKey * ObjectStateEntry -> bool
Public Function TryGetObjectStateEntry (key As EntityKey, ByRef entry As ObjectStateEntry) As Boolean

Parametri

key
EntityKey

Oggetto EntityKey specificato.The given EntityKey.

entry
ObjectStateEntry

Quando termina, questo metodo contiene un oggetto ObjectStateEntry per l'oggetto EntityKey specificato. Questo parametro viene passato senza inizializzazione.When this method returns, contains an ObjectStateEntry for the given EntityKey This parameter is passed uninitialized.

Restituisce

Valore Boolean che è true se è presente un oggetto ObjectStateEntry corrispondente per l'oggetto EntityKey specificato. In caso contrario, false.A Boolean value that is true if there is a corresponding ObjectStateEntry for the given EntityKey; otherwise, false.

Eccezioni

Viene fornito un valore null (Nothing in Visual Basic) per key.A null (Nothing in Visual Basic) value is provided for key.

Esempi

Gli esempi in questo argomento sono basati sul modello Sales di AdventureWorks.The examples in this topic are based on the AdventureWorks Sales Model.

Nell'esempio viene tentato il recupero dell'oggetto ObjectStateEntry corrispondente per l'oggetto EntityKey specificato.The example attempts to retrieve the corresponding ObjectStateEntry for the given EntityKey.

int orderId = 43680;

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    ObjectStateManager objectStateManager = context.ObjectStateManager;
    ObjectStateEntry stateEntry = null;

    var order = (from o in context.SalesOrderHeaders
                 where o.SalesOrderID == orderId
                 select o).First();

    // Attempts to retrieve ObjectStateEntry for the given EntityKey.
    bool isPresent = objectStateManager.TryGetObjectStateEntry(((IEntityWithKey)order).EntityKey, out stateEntry);
    if (isPresent)
    {
        Console.WriteLine("The entity was found");
    }
}
Dim orderId As Integer = 43680

Using context As New AdventureWorksEntities()
    Dim objectStateManager As ObjectStateManager = context.ObjectStateManager
    Dim stateEntry As ObjectStateEntry = Nothing

    Dim order = (From o In context.SalesOrderHeaders
        Where o.SalesOrderID = orderId
        Select o).First()

    ' Attempts to retrieve ObjectStateEntry for the given EntityKey. 
    Dim isPresent As Boolean = objectStateManager.TryGetObjectStateEntry(DirectCast(order, IEntityWithKey).EntityKey, stateEntry)
    If isPresent Then
        Console.WriteLine("The entity was found")
    End If
End Using

Nell'esempio seguente viene utilizzato il metodo TryGetObjectStateEntry(EntityKey, ObjectStateEntry) sull'oggetto ObjectStateManager restituito per ottenere un oggetto in base alla relativa chiave di entità.The following example uses the TryGetObjectStateEntry(EntityKey, ObjectStateEntry) method on the returned ObjectStateManager to get an object based on its entity key.

private static void ApplyItemUpdates(SalesOrderDetail originalItem,
    SalesOrderDetail updatedItem)
{
    using (AdventureWorksEntities context =
        new AdventureWorksEntities())
    {
        context.SalesOrderDetails.Attach(updatedItem);
        // Check if the ID is 0, if it is the item is new. 
        // In this case we need to chage the state to Added.
        if (updatedItem.SalesOrderDetailID == 0)
        {
            // Because the ID is generated by the database we do not need to
            // set updatedItem.SalesOrderDetailID.
            context.ObjectStateManager.ChangeObjectState(updatedItem, System.Data.EntityState.Added);
        }
        else
        {
            // If the SalesOrderDetailID is not 0, then the item is not new
            // and needs to be updated. Because we already added the 
            // updated object to the context we need to apply the original values.
            // If we attached originalItem to the context 
            // we would need to apply the current values:
            // context.ApplyCurrentValues("SalesOrderDetails", updatedItem);
            // Applying current or original values, changes the state 
            // of the attached object to Modified.
            context.ApplyOriginalValues("SalesOrderDetails", originalItem);
        }
        context.SaveChanges();
    }
}
Private Shared Sub ApplyItemUpdates(ByVal originalItem As SalesOrderDetail, ByVal updatedItem As SalesOrderDetail)
    Using context As New AdventureWorksEntities()
        context.SalesOrderDetails.Attach(updatedItem)
        ' Check if the ID is 0, if it is the item is new. 
        ' In this case we need to chage the state to Added. 
        If updatedItem.SalesOrderDetailID = 0 Then
            ' Because the ID is generated by the database we do not need to 
            ' set updatedItem.SalesOrderDetailID. 
            context.ObjectStateManager.ChangeObjectState(updatedItem, System.Data.EntityState.Added)
        Else
            ' If the SalesOrderDetailID is not 0, then the item is not new 
            ' and needs to be updated. Because we already added the 
            ' updated object to the context we need to apply the original values. 
            ' If we attached originalItem to the context 
            ' we would need to apply the current values: 
            ' context.ApplyCurrentValues("SalesOrderDetails", updatedItem); 
            ' Applying current or original values, changes the state 
            ' of the attached object to Modified. 
            context.ApplyOriginalValues("SalesOrderDetails", originalItem)
        End If
        context.SaveChanges()
    End Using
End Sub

Commenti

Utilizzare il metodo TryGetObjectStateEntry(EntityKey, ObjectStateEntry) per restituire un oggetto ObjectStateEntry senza dovere gestire l'eccezione InvalidOperationException generata dal metodo GetObjectStateEntry(EntityKey).Use TryGetObjectStateEntry(EntityKey, ObjectStateEntry) to return an ObjectStateEntry without having to handle the InvalidOperationException raised by the GetObjectStateEntry(EntityKey) method.

TryGetObjectStateEntry(Object, ObjectStateEntry)

Tenta di recuperare l'oggetto ObjectStateEntry corrispondente per l'oggetto Object specificato.Tries to retrieve the corresponding ObjectStateEntry for the specified Object.

public:
 bool TryGetObjectStateEntry(System::Object ^ entity, [Runtime::InteropServices::Out] System::Data::Objects::ObjectStateEntry ^ % entry);
public bool TryGetObjectStateEntry (object entity, out System.Data.Objects.ObjectStateEntry entry);
member this.TryGetObjectStateEntry : obj * ObjectStateEntry -> bool
Public Function TryGetObjectStateEntry (entity As Object, ByRef entry As ObjectStateEntry) As Boolean

Parametri

entity
Object

Oggetto Object a cui appartiene l'oggetto ObjectStateEntry recuperato.The Object to which the retrieved ObjectStateEntry belongs.

entry
ObjectStateEntry

Quando termina, questo metodo contiene l'oggetto ObjectStateEntry per l'oggetto EntityKey specificato. Questo parametro viene passato senza inizializzazione.When this method returns, contains the ObjectStateEntry for the given EntityKey This parameter is passed uninitialized.

Restituisce

Valore booleano che è true se è presente un oggetto ObjectStateEntry corrispondente per l'oggetto specificato. In caso contrario false.A Boolean value that is true if there is a corresponding ObjectStateEntry for the given object; otherwise, false.

Commenti

Utilizzare il metodo TryGetObjectStateEntry(Object, ObjectStateEntry) per restituire un oggetto ObjectStateEntry senza dovere gestire l'eccezione InvalidOperationException generata dal metodo GetObjectStateEntry(Object).Use the TryGetObjectStateEntry(Object, ObjectStateEntry) method to return an ObjectStateEntry without having to handle the InvalidOperationException raised by the GetObjectStateEntry(Object) method.

Si applica a