不支持引用非标量变量

悬赏园豆：50 [已关闭问题] 浏览: 749次

以下是MSDN上面的解析，不太明白“非标量变量“”？

不支持在查询中引用非标量变量（如实体）。在此类查询执行时，会引发 NotSupportedException 异常，并显示以下消息：“无法创建类型为‘EntityType’的常量值。此上下文中仅支持基元类型(‘如 Int32、String 和 Guid’)。”[Unable to create a constantvalue of type 'Closure type'. Only primitive types ('such as Int32,String, and Guid') are supported in this context.]

说明：
支持引用标量变量的集合。

using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
{
    Contact contact = AWEntities.Contacts.FirstOrDefault();

    // Referencing a non-scalar closure in a query will
    // throw an exception when the query is executed.
    IQueryable<string> contacts = from c in AWEntities.Contacts
        where c == contact
        select c.LastName;

    try
    {
        foreach (string name in contacts)
        {
            Console.WriteLine("Name: ", name);
        }
    }
    catch (NotSupportedException ex)
    {
        Console.WriteLine(ex.Message);
    }
}