EntityCollection<TEntity>.Contains(TEntity) 方法

定義

判斷特定物件是否存在集合中。Determines whether a specific object exists in the collection.

public:
 virtual bool Contains(TEntity entity);
public bool Contains (TEntity entity);
abstract member Contains : 'Entity -> bool
override this.Contains : 'Entity -> bool
Public Function Contains (entity As TEntity) As Boolean

參數

entity
TEntity

要在 EntityCollection<TEntity> 中尋找的物件。The object to locate in the EntityCollection<TEntity>.

傳回

Boolean

如果在 EntityCollection<TEntity> 中找到物件,則為 true,否則為 falsetrue if the object is found in the EntityCollection<TEntity>; otherwise, false.

實作

範例

這個範例是以「 艾德作品」銷售模型為基礎。This example is based on the Adventure Works Sales Model. 若要執行此範例中的程式碼,您必須已經將 AdventureWorks Sales Model 加入到專案中,並設定您的專案使用 Entity Framework。To run the code in this example, you must have already added the AdventureWorks Sales Model to your project and configured your project to use the Entity Framework. 若要這樣做,請完成 how to:手動設定 Entity Framework 專案 和 how To:手動定義模型和對應檔中的程式。To do this, complete the procedures in How to: Manually Configure an Entity Framework Project and How to: Manually Define the Model and Mapping Files.

此範例會執行下列各項:This example does the following:

  1. 建立兩個新的 SalesOrderHeader 實體並將它們加入至 Contact 實體。Creates two new SalesOrderHeader entities and adds them to the Contact entity.

  2. 從與 Contact 實體相關聯的 RelationshipManager 中取得所有相關端。Gets all related ends from the RelationshipManager that is associated with the Contact entity.

  3. 逐一查看 IRelatedEnd 的集合。Iterates through the collection of IRelatedEnds.

  4. 取得每個相關端的 EntityCollection<TEntity>Gets the EntityCollection<TEntity> for each related end.

  5. 使用 Remove 方法,從集合中移除其中一個實體。Uses the Remove method to remove one of the entities from the collection.

  6. 呼叫 Contains 方法來判斷此物件是否已經從集合中移除了。Calls the Contains method to determine whether the object was removed from the collection.

  7. 使用 Add 方法來重新加入實體。Uses the Add method to add the entity back.

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    Contact contact = new Contact();

    // Create a new SalesOrderHeader.
    SalesOrderHeader newSalesOrder1 = new SalesOrderHeader();
    // Add SalesOrderHeader to the Contact.
    contact.SalesOrderHeaders.Add(newSalesOrder1);

    // Create another SalesOrderHeader.
    SalesOrderHeader newSalesOrder2 = new SalesOrderHeader();
    // Add SalesOrderHeader to the Contact.
    contact.SalesOrderHeaders.Add(newSalesOrder2);

    // Get all related ends
    IEnumerable<IRelatedEnd> relEnds =
        ((IEntityWithRelationships)contact)
        .RelationshipManager.GetAllRelatedEnds();

    foreach (IRelatedEnd relEnd in relEnds)
    {
        // Get Entity Collection from related end
        EntityCollection<SalesOrderHeader> entityCollection =
            (EntityCollection<SalesOrderHeader>)relEnd;

        Console.WriteLine("EntityCollection count: {0}",
            entityCollection.Count);
        // Remove the first entity object.
        entityCollection.Remove(newSalesOrder1);

        bool contains = entityCollection.Contains(newSalesOrder1);

        // Write the number of items after one entity has been removed
        Console.WriteLine("EntityCollection count after one entity has been removed: {0}",
            entityCollection.Count);

        if (contains == false)
            Console.WriteLine("The removed entity is not in in the collection any more.");

        //Use IRelatedEnd to add the entity back.
        relEnd.Add(newSalesOrder1);
        Console.WriteLine("EntityCollection count after an entity has been added again: {0}",
            entityCollection.Count);
    }
}
Using context As New AdventureWorksEntities()
    Dim contact As New Contact()

    ' Create a new SalesOrderHeader. 
    Dim newSalesOrder1 As New SalesOrderHeader()
    ' Add SalesOrderHeader to the Contact. 
    contact.SalesOrderHeaders.Add(newSalesOrder1)

    ' Create another SalesOrderHeader. 
    Dim newSalesOrder2 As New SalesOrderHeader()
    ' Add SalesOrderHeader to the Contact. 
    contact.SalesOrderHeaders.Add(newSalesOrder2)

    ' Get all related ends 
    Dim relEnds As IEnumerable(Of IRelatedEnd) = DirectCast(contact, IEntityWithRelationships).RelationshipManager.GetAllRelatedEnds()

    For Each relEnd As IRelatedEnd In relEnds
        ' Get Entity Collection from related end 
        Dim entityCollection As EntityCollection(Of SalesOrderHeader) = DirectCast(relEnd, EntityCollection(Of SalesOrderHeader))

        Console.WriteLine("EntityCollection count: {0}", entityCollection.Count)
        ' Remove the first entity object. 
        entityCollection.Remove(newSalesOrder1)

        Dim contains As Boolean = entityCollection.Contains(newSalesOrder1)

        ' Write the number of items after one entity has been removed 
        Console.WriteLine("EntityCollection count after one entity has been removed: {0}", entityCollection.Count)

        If contains = False Then
            Console.WriteLine("The removed entity is not in in the collection any more.")
        End If

        'Use IRelatedEnd to add the entity back. 
        relEnd.Add(newSalesOrder1)
        Console.WriteLine("EntityCollection count after an entity has been added again: {0}", entityCollection.Count)
    Next
End Using

備註

使用 Object.Equals 方法來比較指定的物件與已經位於集合中的物件。Uses the Object.Equals method to compare the specified object with the objects already in the collection.

適用於