Question

我有一个像

这样的表格

Application_OID
Status
{some other fields}
RecommendedFromApplication_OID

RecommendedFromApplication_OID将包含上次推荐的对象的Application_OID。例如，有一个应用程序

Application_OID = 1
Status = New
{some other fields}
RecommendedFromApplication_OID = null

建议将此应用程序用于其他作业，使用以下值创建另一个应用程序

Application_OID = 2
Status = New
{some other fields}
RecommendedFromApplication_OID = 1

并且第一个对象的状态将更新为

Application_OID = 1
Status = Recommended
{some other fields}
RecommendedFromApplication_OID = null

假设我推荐新创建的另一个作业，将使用以下值创建一个新条目

Application_OID = 3
Status = New
{some other fields}
RecommendedFromApplication_OID = 2

第二个应用程序将更新为推荐，最终数据将

Application_OID = 1
Status = Recommended
{some other fields}
RecommendedFromApplication_OID = null

Application_OID = 2
Status = Recommended
{some other fields}
RecommendedFromApplication_OID = 1

Application_OID = 3
Status = New
{some other fields}
RecommendedFromApplication_OID = 2

通过这种方式，我可以推荐一个我想要的应用程序。

现在问题;我想在LINQ中编写一个函数，它将获取Application_OID并返回包含所有推荐（子）应用程序的Application_OID的ID的List，如

private List<int> GetRecommendedIds(int id)
{
    var applicationIds = (/*some query*/).ToList();
    return applicationIds;
}

然后调用

GetRecommendedIds(1)

将返回值为

的int列表

2,3

Answer 1

public List<int> GetRecommendedForApplication(int Application_OID)
    {
        var recommendedApplications = new List<int>();
        var context = new SomeEntities();
        int applicationId = Application_OID;
        Application application;
        do
        {
            application = (from applications in context.Applications
                           join recommendedApplication in context.Applications
                               on applications.Application_OID equals
                               recommendedApplication.ParentApplication_OID
                               where recommendedApplication.ParentApplication_OID == applicationId
                           select recommendedApplication.Application_OID).FirstOrDefault();
            if (application != null)
            {
                recommendedApplications.Add(application);
                applicationId = application.Application_OID;
            }
        } while (application != null && application.ParentApplication_OID != null);

        return recommendedApplications;
    }

LINQ for（递归或不递归）从父母开始寻找所有孩子

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