简单联合查询

new DBHelper<DTStudentModel>()
.Select(p => new
{
    p.StuCode,
    p.StuName,
    p.StuSex
})
.Union<DTStudentModel>(new DBHelper<DTStudentModel>().Select(p => new { p.StuCode, p.StuName, p.StuSex }).Where(p => p.StuSex == "女"))
.Where(p => p.StuSex == "男")
.ToEntityList<DTStudentModel>();
-- 对应 SQL
select [T_Student].[StuCode],[T_Student].[StuName],[T_Student].[StuSex] from [T_Student] where ([T_Student].[StuSex] = '男') union (select [T_Student].[StuCode],[T_Student].[StuName],[T_Student].[StuSex] from [T_Student] where ([T_Student].[StuSex] = '女'))