无法使用Session.BeginTransaction设置IsolationLevel.ReadUncommitted

Question

我尝试使用下一个代码设置IsolationLevel.ReadUncommitted

public class EntityRepository : RepositoryBase<Entity>, IEntityRepository
{
...
    public void SomeFunction()
    {
        using (var transaction = Session.BeginTransaction(IsolationLevel.ReadUncommitted))
        {
            // Profiler log: set transaction isolation level read committed
            try
            {
                Session.Query<Entity>().Count();
                // Profiler log: select count(*) from dbo.Entity
                transaction.Commit();
            }
            catch
            {
                transaction.Rollback();
                throw;
            }
        }
    }
...
}

但是我的Profiler说查询是在隔离级读取已提交的情况下执行的。

如果SomeFunction替换为

public void SomeFunction()
{
    // 1. set isolation level uncommeted
    using (var transaction = Session.BeginTransaction(IsolationLevel.ReadUncommitted))
    {
        // Profiler log: set transaction isolation level read committed
        try
        {
            transaction.Commit();
        }
        catch
        {
            transaction.Rollback();
            throw;
        }
    }

    // 2. execute query
    Session.Query<Entity>().Count();
    // Profiler log: set transaction isolation level read uncommitted
    // Profiler log: select count(*) from dbo.Entity

    // 3. set isolation level committed
    using (var transaction = Session.BeginTransaction(IsolationLevel.ReadCommitted))
    {
        // Profiler log: set transaction isolation level read uncommitted
        try
        {
            transaction.Commit();
        }
        catch
        {
            transaction.Rollback();
            throw;
        }
    }
}

查询与IsolationLevel.ReadUncommitted的调用。 步骤1.为会话设置readuncommitted隔离级别。 步骤2.调用我的查询，隔离级别readuncommitted。 步骤3.将会话隔离级别设置为readcommitted。

为什么会这样？ 如何解决？

FluentNHibernate 1.3.0.733