EntityCollection<TEntity>.Add(TEntity) 方法

public:
 virtual void Add(TEntity entity);

public void Add(TEntity entity);

override this.Add : 'Entity -> unit

Public Sub Add (entity As TEntity)

参数

实现

例外

示例

此示例基于 Adventure Works 销售模型。 若要运行此示例中的代码，必须将 AdventureWorks 销售模型添加到项目中，并将项目配置为使用 Entity Framework。 为此，请完成 如何：手动配置 Entity Framework Project 和 如何：手动定义模型和映射文件。

此示例创建两个新 SalesOrderHeader 实体，将其添加到 Contact 实体，在删除对象后，使用 Add 该方法将对象添加回集合。

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)
            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);
    }
}

注解

该方法 Add 将对象添加到两 EntityCollection<TEntity> 个对象之间并创建关系。 当源对象附加到ObjectContext实例时，Add该方法还会将对象添加到 .ObjectContext 调用时 SaveChanges ，此操作将转换为数据源中的插入操作。 有关详细信息，请参阅 创建、添加、修改和删除对象。

Add可以在同一对象实例上多次调用该方法。