ObjectStateManager.TryGetObjectStateEntry 方法

定義

命名空間:

System.Data.Objects

組件:

System.Data.Entity.dll

嘗試回傳 ObjectStateEntry 特定物件或關聯項目的物件。

多載

名稱	Description
TryGetObjectStateEntry(EntityKey, ObjectStateEntry)	嘗試取得與指定EntityKey物件或關係的對應 ObjectStateEntry 。
TryGetObjectStateEntry(Object, ObjectStateEntry)	嘗試取得 ObjectStateEntry 對應 Object的 。

TryGetObjectStateEntry(EntityKey, ObjectStateEntry)

嘗試取得與指定EntityKey物件或關係的對應 ObjectStateEntry 。

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

參數

key

EntityKey

給定 EntityKey的。

entry

ObjectStateEntry

當此方法回傳時，包含 ObjectStateEntry 對給定 EntityKey 的 ，此參數未初始化。

傳回

Boolean

一個布林值，若true存在對應ObjectStateEntry的給定EntityKey;否則，。 false

例外狀況

ArgumentNullException

key 提供 null（Visual Basic 中為 Nothing）值。

範例

以下範例嘗試檢索給定 EntityKey的對應 ObjectStateEntry 。

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");
    }
}

以下範例使用 TryGetObjectStateEntry(EntityKey, ObjectStateEntry) 了 返回 上 ObjectStateManager 的方法，根據其實體鍵數取得物件。

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();
    }
}

備註

用TryGetObjectStateEntry(EntityKey, ObjectStateEntry)來退貨，ObjectStateEntry無需處理該方法的提升InvalidOperationExceptionGetObjectStateEntry(EntityKey)。

TryGetObjectStateEntry(Object, ObjectStateEntry)

嘗試取得 ObjectStateEntry 對應 Object的 。

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

參數

entity

Object

Object取回ObjectStateEntry者所屬的。

entry

ObjectStateEntry

當此方法回傳時，包含 ObjectStateEntry 給定 EntityKey 參數，該參數未初始化。

傳回

Boolean

一個布林值，若存在對應ObjectStateEntry的物件，則為true;否則，。 false

備註

使用TryGetObjectStateEntry(Object, ObjectStateEntry)該方法來返回，ObjectStateEntry而無需處理該方法所GetObjectStateEntry(Object)提出的部分InvalidOperationException。