Linq 列表列表到一个列表

Question

我有一个 Linq 查询，可以像这样更新每个条件组中的第一项

var results = StudentsList.GroupBy(x => x.GroupID)
    .Where(g => !g.Any(p => p.Student == "Adam") && g.Any(x => x.University == "OPQ"))
    .Select(g => 
            {
                var firstItem = g.First(x => x.University == "OPQ");
                firstItem.IsQualified = true;

                return firstItem;
            }).ToList();

在保留原有功能的同时，我想另外-

• 如果存在，请使用University!= "OPQ" 和Course= "HR"（第2 组）为同一组中的所有学生更新IsQualified= true。如果不存在，则忽略（第 5 组）

输出

• Donald、Silver、Emity（所有第 2 组）和 White（第 5 组）。

我尝试了什么

在"firstItem.IsQualified = true;" 行下方，我添加了-

var otherItems=g.Any(x=>x.University != "OPQ" && x.Course =="HR");
otherItems.IsQualified= true;

我的代码

    List<StudentInfo> StudentsList = new List<StudentInfo>();

    // Group 1
    StudentsList.Add( new StudentInfo { Student="Gungun", University="cdf", Course="GD", GroupID = 1, IsQualified=false});
    StudentsList.Add( new StudentInfo { Student="John", University="abc", Course="ACC", GroupID = 1, IsQualified=false});
    StudentsList.Add( new StudentInfo { Student="Jack", University="def", Course="CS", GroupID = 1, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Peter", University="abc", Course="GD", GroupID = 1, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Lemity", University="abc", Course="CS", GroupID = 1, IsQualified=false} );

    // Group 2
    StudentsList.Add( new StudentInfo { Student="Donald", University="def", Course="HR",GroupID = 2, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Olivia", University="ggh", Course="RC",GroupID = 2, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Silver", University="tcs", Course="HR",GroupID = 2, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Carl", University="yyz", Course="AC",GroupID = 2, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Emity", University="OPQ", Course="AC",GroupID = 2, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Emma", University="OPQ", Course="GD", GroupID = 2, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Alan", University="OPQ", Course="GD", GroupID = 2, IsQualified=false} );

    // Group 3
    StudentsList.Add( new StudentInfo { Student="Adam", University="yub", Course="CS", GroupID = 3, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Jacob", University="OPQ", Course="AC",GroupID = 3, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Matthew", University="OPQ", Course="HR", GroupID = 3, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Saint", University="abc", Course="MNGT",  GroupID = 3, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Joshua", University="qer", Course="MNGT",  GroupID = 3, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Aubrey", University="fef", Course="MNGT",  GroupID = 3, IsQualified=false} );

    // Group 4
    StudentsList.Add( new StudentInfo { Student="Caleb", University="DEF", Course="HR", GroupID = 4, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Anna", University="ABC", Course="HR", GroupID = 4, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Chill", University="GHI", Course="GD", GroupID = 4, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Alexis", University="JKL", Course="CS", GroupID = 4, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="Zoe", University="MNO", Course="MNGT", GroupID = 4, IsQualified=false} );

    // Group 5
    StudentsList.Add( new StudentInfo { Student="Dylan", University="PQR", Course="ACC", GroupID = 5, IsQualified=false} );
    StudentsList.Add( new StudentInfo { Student="White", University="OPQ", Course="CE", GroupID = 5, IsQualified=false} );

public class StudentInfo
{
  public string Student { get; set; }
  public string University { get; set; }
  public string Course { get; set; }
  public int GroupID { get; set; }
  public bool IsQualified {get; set;}
}

Answer 1

Demo on dotnet fiddle

不用.Select()，也可以用SelectMany来实现。

    var results = StudentsList.GroupBy(x => x.GroupID)
                              .Where(g => !g.Any(p => p.Student == "Adam") && g.Any(x => x.University == "OPQ"))
                              .SelectMany(g => 
                                    {
                                        var firstItem = g.First(x => x.University == "OPQ");
                                        firstItem.IsQualified = true;

                                        var otherItems = g.Where(x => x.University != "OPQ" && x.Course == "HR")
                                                          .Select(z => 
                                                                  {
                                                                      var item = z;
                                                                      item.IsQualified = true;
                                                                      return item;
                                                                  }).ToList();
                                        otherItems.Add(firstItem);
                                        return otherItems;
                                    }).ToList();

输出

Group:2 Student:Donald IsQualified:True
Group:2 Student:Silver IsQualified:True
Group:2 Student:Emity IsQualified:True
Group:5 Student:White IsQualified:True

Answer 2

你可以试试这个：

        var otherItems = StudentsList.Where(x => x.University != "OPQ" && x.Course == "HR");
        foreach (var otherItem in otherItems)
        {
            otherItem.IsQualified = true;
        }