Nhibernate强制nvarchar查询

Question

我怎么能强制Nhibernate将字符串替换为nvarchar而不是使用条件等于varchar？

我有这段代码

        var permissionCriteria = DetachedCriteria.For<Permission>("p")
            .SetProjection(Projections.Id())
            .Add(Restrictions.Eq("UserId", user.UserId))
            .Add(Expression.EqProperty("p.TypeId", "T.Id"));

在以下sql中翻译

 and exists (SELECT this_0_.Id as y0_
               FROM   Permissions this_0_
               WHERE  this_0_.UserId = 'USERNAME'/* @p5 */
                      and this_0_.TypeId = t2_.Id);

问题是“USERNAME”之前缺少“N”导致sql server进行扫描而不是搜索。

属性UserId由NH更正地映射到nvarchar，但它仍然用作ANSI字符串

修改 这是班级

     public class Permission : EntityBase
     {
        public virtual string Id { get; set; }          
        public virtual string UserId { get; set; }

        ....
     }

和映射

public class PermissionOverrides : IAutoMappingOverride<Permission>
{
    public void Override(AutoMapping<Permission> mapping)
    {
        mapping.Table("Permissions");
        mapping.Id(x => x.Id).GeneratedBy.Assigned();
        mapping.Map(x => x.UserId);
        ....
    }
 }

我也试过

        mapping.Map(x => x.UserId).CustomSqlType("nvarchar(20)");

没有运气