ObjectContext.ObjectStateManager 属性

定义

获取对象上下文用于跟踪对象更改的对象状态管理器。Gets the object state manager used by the object context to track object changes.

public:
 property System::Data::Objects::ObjectStateManager ^ ObjectStateManager { System::Data::Objects::ObjectStateManager ^ get(); };
public System.Data.Objects.ObjectStateManager ObjectStateManager { get; }
member this.ObjectStateManager : System.Data.Objects.ObjectStateManager
Public ReadOnly Property ObjectStateManager As ObjectStateManager

属性值

ObjectStateManager

ObjectStateManager 使用的 ObjectContextThe ObjectStateManager used by this ObjectContext.

示例

这些示例基于 Microsoft SQL Server 产品示例:数据库These examples are based on the Microsoft SQL Server Product Samples: Database. 此示例从 ObjectStateManager 获取 ObjectContext,并使用状态管理器访问上下文中的对象。This example gets the ObjectStateManager from the ObjectContext and uses the state manager to access an object in the context.

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

此示例对返回的 TryGetObjectStateEntry 使用 ObjectStateManager 方法基于对象的实体键获取对象。This example uses the TryGetObjectStateEntry 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

适用于