Question

给出以下c＃代码：

public class Class1
{
    public static void Main()
    {

        var tasks = new[]
        {
            new Task {id = 1, name = "Task 1", dependencyId = 0},
            new Task {id = 2, name = "Task 2", dependencyId = 1},
            new Task {id = 3, name = "Task 3", dependencyId = 2},
            new Task {id = 4, name = "Task 4", dependencyId = 3},
            new Task {id = 5, name = "Task 5", dependencyId = 0},
        };

        var listOfTasks = (from t in tasks
                 join dt in tasks
                     on t.id equals dt.dependencyId into JoinedTasks
                 from jt in JoinedTasks
                 select new TaskWithDependency
                    {
                        Task = jt,
                        DependentTask = t
                    }).ToList();

        foreach (var z in listOfTasks)
        {
            Console.WriteLine(z.Task.name + " depends on: " + (z.DependentTask != null ? z.DependentTask.name : ""));
        }
        Console.ReadKey();

    }
}

public class TaskWithDependency
{
    public Task Task { get; set; }
    public Task DependentTask { get; set; }
}

public class Task
{
    public int id { get; set; }
    public string name { get; set; }
    public int dependencyId { get; set; }
}

如何使用LINQ投射到IEnumerable<TaskWithDependency>。我正在有效地尝试实现自我加入。结果应该是IEnumerable<TaskWithDependency>，在此示例中，只有第一个TaskWithDependency具有依赖关系。

Answer 1

var tasksTransformed = tasks.Select(x => new TaskWithDependency
{
    Task = x,
    DependentTask = tasks.Where(y => y.DependencyId == x.id)
}

Answer 2

这可能是您正在寻找的：

IEnumerable<TaskWithDependency> tasksWithDep = tasks.Select(t => new TaskWithDependency() { Task = t, DependentTask = tasks.Where(dt => dt.dependencyId == t.id) });

自我引用LINQ

2 个答案: