ObjectStateManager.TryGetObjectStateEntry 方法

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

参数

返回

一个布尔值，该值为true给定的对应ObjectStateEntryEntityKey值;否则为 false。

例外

示例

下面的示例尝试检索给定EntityKey的对应ObjectStateEntry项。

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");
    }
}

下面的示例使用 TryGetObjectStateEntry(EntityKey, ObjectStateEntry) 返回 ObjectStateManager 的方法根据其实体键获取对象。

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();
    }
}

注解

用于 TryGetObjectStateEntry(EntityKey, ObjectStateEntry) 返回一个 ObjectStateEntry ，而无需处理 InvalidOperationException 方法引发的 GetObjectStateEntry(EntityKey) 函数。

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

参数

返回

一个布尔值，如果 true 给定对象有相应的 ObjectStateEntry 值，则为 ;否则为 false。

注解

TryGetObjectStateEntry(Object, ObjectStateEntry)使用该方法可返回一个ObjectStateEntry，而无需处理InvalidOperationException该方法引发的GetObjectStateEntry(Object)函数。