循環遞歸自聯接表

Question

我有以下SQL Server表結構，它是一個邏輯樹文件夾結構。

我正在使用Linq to SQL with SQL Server。

我想要做的是循環並在內存上創建文件夾結構，從Root的層次文件夾，所有子項的主要父項。

我試圖用一些foreach循環來做，但我仍然沒有得到它。 我想我必須使用某種遞歸方式。

我嘗試了一些查詢：

var flds = from folders in repo.Folders
                                   join folders2 in repo.Folders on folders.Id equals folders2.idParent
                                   select folders;

我的目標是迭代該文件夾邏輯結構。

Answer 1

如果要將文件夾作為表中給出的層次結構，可以像這樣創建它：

    var tableData = repo.Folders.ToList();
    var directories = tableData.Select(f => GetPath(f, table));

正如您所問，創建文件夾層次結構的遞歸方法是：

    private static string GetPath(Folder f)
    {
        if (f.IdParent == 0)
        {
            return f.Name;
        }
        else
        {
            var parent = tableData.Find(d => d.Id == f.IdParent);
            return GetPath(parent) + "|" + f.Name;
        }
    }

你會得到這樣的輸出：

它會給你一個完整的文件夾hirarchy，我不知道你想如何使用它。 所以你可以根據需要做一些修改。 希望能幫助到你！

這里我添加代碼來迭代並創建文件夾結構：

        foreach (var dir in directories)
        {
            var folders = dir.Split('|');
            var path = string.Empty;
            foreach (var folder in folders)
            {
                path = path + "\\" + folder;  // modify the path like '\\' if it is not valid I have not tested
                CreateFolder(path); // implement this method for actual creation of folders
            }
        }

以及創建文件夾的方法：

private static void CreateFolder(string directory)
    {
        var path = "C:" + directory; // add whenever you want to create structure
        if (!Directory.Exists(path))
        {
            Directory.CreateDirectory(path);
        }
    }

Answer 2

你可以嘗試這個：

// Get a list of the folders.
// We do this, in order to avoid the performance hit, that Panagiotis 
// pointed out correctly in his comment.
var folders = repo.Folders.ToList();

// Get the root folder.
var rootFolder = folders.Where(x=>x.idParent==null).SingleOrDefault();

// Group the folders by their parentId.
var groupedFolders = from folder in folders
                     where folder.idParent!=null
                     orderby folder.idParent ascending
                     group folder by folder.idParent into grp
                     select new
                     {
                         ParentFolderId = grp.Key,
                         Folders = grp.Select(x=>x)
                     };

// Print the name of the root folder.
Console.WriteLine("Root Folder", rootFolder.Name);

// Iterate through the groups of folders. 
foreach(var grp in groupedFolders)
{
    // Get the name of the parent folder for the current group.
    string parentFolderName = folders.Where(x=>x.Id==grp.ParentFolderId)
                                     .Single(x=>x.Name);


    // Print the name of the parent folder.
    Console.WriteLine("Parent Folder", parentFolderName);

    // Iterate through the folders of the current group.
    foreach(var folder in grp.Folders)
    {
        Console.WriteLine(folder.Name);
    }
}