代码，注意值的顺序不同。因此，它在锁定行之间交替：

static void Main( string[] args )
        {
            List<int> list = new List<int>();

            for(int i = 0; i < 1000; i++ )
                list.Add( i );

            Parallel.ForEach( list, i =>
            {
                using( NamePressDataContext db = new NamePressDataContext() )
                {
                    db.ExecuteCommand( @"update EBayDescriptionsCategories set CategoryId = Ids.CategoryId from EBayDescriptionsCategories 
                        join (values (7276, 20870),(240, 20870)) as Ids(Id,CategoryId) on Ids.Id = EBayDescriptionsCategories.Id" );

                    db.ExecuteCommand( @"update EBayDescriptionsCategories set CategoryId = Ids.CategoryId from EBayDescriptionsCategories 
                        join (values (240, 20870),(7276, 20870)) as Ids(Id,CategoryId) on Ids.Id = EBayDescriptionsCategories.Id" );
                }

            } ); 
        }

表def：

CREATE TABLE [dbo].[EDescriptionsCategories](
    [CategoryId] [int] NOT NULL,
    [Id] [int] NOT NULL,
 CONSTRAINT [PK_EDescriptionsCategories] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)

例外：

Transaction (Process ID 80) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

该代码仅与WITH（TABLOCK）提示一起使用。是否可能不仅仅为了并行更新那两行就锁定整个表？