Linq 除了两个 IEnumerable 查询

Question

我有一个返回 IEnumerable 类型的两个 linq 查询。第一个查询返回过滤值，第二个查询返回我想要的所有值，除了从第二个查询到第一个查询（如 SQL 中的减号运算符）并绑定到我的列表框。

我的代码示例 =>

using (ISession session = SessionManager.CurrentSession)
        {
            IEnumerable<RoleDefinition> roleAssigned = from groupRole in session.Query<GroupRole>()
                join roleDef in session.Query<RoleDefinition>() on groupRole.RoleDefinitionId equals
                    roleDef.RoleDefinitionId
                where groupRole.GroupId == SelectedGroupId
                orderby roleDef.RoleName
                select new RoleDefinition
                {
                    RoleName = roleDef.RoleName
                };

            IEnumerable<RoleDefinition> roleUnassigned = from grole in session.Query<RoleDefinition>()
                orderby grole.RoleName
                select new RoleDefinition
                {
                    RoleName = grole.RoleName
                };

            List<RoleDefinition> lRoleAss = roleAssigned.ToList();
            List<RoleDefinition> lRoleUnAss = roleUnassigned.ToList();
            lRoleUnAss = lRoleUnAss.Where(x => !lRoleAss.Contains(x)).ToList();

            lsbAssigned.DataSource = lRoleAss;
            lsbAssigned.TextField = "RoleName";
            lsbAssigned.ValueField = "RoleName";
            lsbAssigned.DataBind();

            lsbUnAssigned.DataSource = lRoleUnAss;
            lsbUnAssigned.TextField = "RoleName";
            lsbUnAssigned.ValueField = "RoleName";
            lsbUnAssigned.DataBind();
        }

EDIT => 我修复了如下代码，并且我的功能成功运行

      List<RoleDefiniton> filteredUnassign = lRoleUnAss.Where(def => !lRoleAss.Select(x => x.RoleName).Contains(def.RoleName)).ToList();

Answer 1

更改以下行：

lRoleUnAss = lRoleUnAss.Where(x => !lRoleAss.Contains(x)).ToList();

到

var results = lRoleUnAss.Except(lRoleAss).ToList();

并使用results 获取最终列表。

我声明了一个新变量，因为我不知道您是否要保持初始列表不变。如果您不介意更改它，您可以尝试：

lRoleUnAss = lRoleUnAss.Except(lRoleAss).ToList();