如何在不同实体中复用相同的Where子句？

业务场景 #

在我的应用中，已登录的管理员用户需根据权限查看「合作伙伴」，基础实现代码如下：

public async Task<IList<Partner>> GetPartners(IList<Permission> permissions, Admin admin)
{
    bool all = permissions.Any(x => x.Key == "SeePartners" && x.Value == "All");
    bool sameArea = permissions.Any(x => x.Key == "SeePartners" && x.Value == "SameArea");

    var p = _dbContext.Partners.Where(x => all || (sameArea && x.AreaId == admin.AreaId));

    return await p.AsNoTracking().ToListAsync();
}

每个合作伙伴关联不同项目，管理员查看项目关联的合作伙伴时，仍需遵循相同的权限规则，基础实现代码如下：

public async Task<IList<ProgramPartner>> GetProgramPartners(IList<Permission> permissions, Admin admin, Guid programId)
{
    bool all = permissions.Any(x => x.Key == "SeePartners" && x.Value == "All");
    bool sameArea = permissions.Any(x => x.Key == "SeePartners" && x.Value == "SameArea");

    var p = _dbContext.ProgramPartners.Where(x => x.ProgramId == programId && 
        (all || (sameArea && x.Partner.AreaId == admin.AreaId))
    );

    return await p.AsNoTracking().ToListAsync();
}

需求与尝试 #

由于实际权限逻辑比示例复杂得多，我希望复用权限过滤的Where子句，避免重复代码。

我尝试编写返回布尔值的过滤方法，但EF Core无法将自定义方法翻译为SQL，执行时报错：

public bool FilterPartners(Partner partner, IList<Permission> permissions, Admin admin)
{
    bool all = permissions.Any(x => x.Key == "SeePartners" && x.Value == "All");
    bool ownArea = permissions.Any(x => x.Key == "SeePartners" && x.Value == "OwnArea");

    return all || (ownArea && partner.AreaId == admin.AreaId);
}

public async Task<IList<Partner>> GetPartners(IList<Permission> permissions, Admin admin)
{
    var p = _dbContext.Partners.Where(x => FilterPartners(x, permissions, admin));

    return await p.AsNoTracking().ToListAsync();
}

public async Task<IList<ProgramPartner>> GetProgramPartners(IList<Permission> permissions, Admin admin, Guid programId)
{
    var p = _dbContext.ProgramPartners.Where(x => x.ProgramId == programId)
                                      .Where(x => FilterPartners(x.Partner, permissions, admin));

    return await p.AsNoTracking().ToListAsync();
}

我还尝试过传递IQueryable以及使用Expression函数，但都没成功。

提问 #

这种复用权限过滤Where子句的需求是否可行？如果可行，正确的实现方式是什么？

内容的提问来源于stack exchange，提问作者Mads