c#-如何從子c#遞回獲取所有父母？

有所有的視圖位置（假設有 100 個，這些是 TreeView 的位置）： Id, Name, ParentId 1 Root Null 2 Semi-root 1 3 Semi-semi-root 2 4 ..... ....

并且有些資料中我們僅從另一個請求中接收到與我們的值相對應的那些位置：Id、Name、ParentId 22 Location1 12 36 Location38 21 99 Location38 3

需要獲取我們從請求中獲得的資料的所有父層次結構。有這樣的課：

public class TreeViewNode {
  public Guid Id {get; set;}
  public string Name {get; set;}
  public Guid ParentId {get; set;}
}

測驗資料：

 private IEnumerable<TreeViewNode> SeedData()
        {
            return new List<TreeViewNode>
            {
                new()
                {
                    Id = 1,
                    Name = "Root",
                    ParentId = null
                },
                new()
                {
                    Id = 2,
                    Name = "Semi-root",
                    ParentId = 1
                },
                new()
                {
                    Id = 3,
                    Name = "Semi te",
                    ParentId = 2
                },
                new()
                {
                    Id = 4,
                    Name = "Semi oi",
                    ParentId = 2
                },
                new()
                {
                    Id = 5,
                    Name = "Child",
                    ParentId = 3
                },
                new()
                {
                    Id = 6,
                    Name = "Child 1",
                    ParentId = 4
                },
                new()
                {
                    Id = 7,
                    Name = "Child 2",
                    ParentId = 1
                },
                new()
                {
                    Id = 8,
                    Name = "Child 3",
                    ParentId = 1
                },
                new()
                {
                    Id = 9,
                    Name = "Child 4",
                    ParentId = 1
                },
                new()
                {
                    Id = 10,
                    Name = "Child 6",
                    ParentId = 2
                }
            };
        }

從請求中獲取的示例資料：

 var dataFromRequest = new List<TreeViewNode>
            {
                new()
                {
                    Id = 8,
                    Name = "Child 3",
                    ParentId = 1
                },
                new()
                {
                    Id = 10,
                    Name = "Child 6",
                    ParentId = 2
                },
                new()
                {
                    Id = 33,
                    Name = "Child",
                    ParentId = 3
                },
                new()
                {
                    Id = 4,
                    Name = "Semi oi",
                    ParentId = 2
                }
            };

結果需要得到這樣的父母名單：

Id Name ParentId
1 Root Null
2 Semi-root 1
3 Semi te 2

這里可以有 5 個或更多級別的父母

uj5u.com熱心網友回復：

像這樣的東西

// create Dictionary for lookups
var lookup = dataFromRequest.ToDictionary(x => x.Id.Value, x => x);

var lookFor = new TreeViewNode()
{
    Id = 6,
    Name = "Child 1",
    ParentId = 4
};

// get all the parents
GetParents(lookup, lookFor);

獲取所有父母的幫手方法

private void GetParents(Dictionary<int, TreeViewNode> lookup, 
                                TreeViewNode lookFor)
{
    while (lookFor != null)
    {
        // Alternative: Add lookFor to List<TreeViewNode> here and return at 
        // the end of the method
        Debug.WriteLine($"{lookFor.Id} {lookFor.Name} {lookFor.ParentId}");

        if (lookFor.ParentId == null)
            break;

        // cast ParentId to corrent dataType here Guid or int
        lookup.TryGetValue((int)lookFor.ParentId, out var parentNode);
        lookFor = parentNode;
    }

}

當你得到更多時，記得保持你的查找字典是最新的 IEnumerable<TreeViewNode>

您可以做的另一件事是將父節點設定為TreeViewNode如下所示：

public class TreeViewNode {
    ...
    // set ParentNode by lookup in the Dictionary once
    public TreeViewNode ParentNode {get; set;}
}

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