动态或子句Linq [英] Dynamic Or Clause Linq

问题描述

今天我们目前有这样的声明:

Today we currently have a statement like this:

var Query = (from dp in db.Patients
            select dp);

var UserID = User.Identity.GetUserId();

if (User.IsInRole("Administrator"))
{
    Query = Query.Where(x => x.AdministratorID == UserID);
}
if (User.IsInRole("Counselor"))
{
    Query = Query.Where(x => x.CounselorID == UserID);
}
if (User.IsInRole("Physician"))
{
    Query = Query.Where(x => x.PhysicianID == UserID);
}

问题是我们有可以担任多个角色的用户.如果用户既是辅导员又是医师，我们希望系统撤回所有CounselorID == UserID或PhysicianID == UserID的患者.

The problem is we have Users that can have multiple roles. If a User is both an Counselor and Physician we want the system to pull back all patients where CounselorID == UserID or PhysicianID == UserID.

如果我们不知道页面加载时用户将扮演什么角色，该如何动态完成?

当前.Where子句仅使用 AND 语句，我们需要一个 OR 语句.

The current .Where clause just uses an AND statement we need an OR statment.

理想情况下会有这样的解决方案:

Ideally there would be a solution like this:

if (User.IsInRole("Administrator"))
{
     Query = Query.Where(x => x.AdministratorID == UserID);
}
if (User.IsInRole("Counselor"))
{
     Query = Query.WhereOr(x => x.CounselorID == UserID);
}
if (User.IsInRole("Physician"))
{
     Query = Query.WhereOr(x => x.PhysicianID == UserID);
}

推荐答案

您可以逐步构建谓词.

Func<Pantient, bool> predicate = p => false;

if (User.IsInRole("Administrator"))
{
    var oldPredicate = predicate;
    predicate = p => oldPredicate(p) || p.AdministratorID == UserID;
}

if (User.IsInRole("Counselor"))
{
    var oldPredicate = predicate;
    predicate = p => oldPredicate(p) || p.CounselorID == UserID;
}


var query = db.Patients.Where(predicate);

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