Question

我构建了一个简单的文件管理器，它从两个表，文件夹和文件中提取数据。上传文件时，它会写入服务器上的磁盘。当我需要删除文件夹及其所有子文件夹，子文件夹文件和父文件夹文件时，我选择文件夹，然后单击删除，执行下面的控制器操作。

更新如果我将任何后续调用更改为.ToList（），则可以正常工作。

    [HttpPost]
    public JsonResult DeleteFolder(int folderID)
    {
        var repo = new FileManagerRepository();

        var folder     = repo.GetFolder(folderID);
        var subfolders = repo.GetSubFolders(folderID).ToList();
        var files      = repo.GetFiles(folderID).ToList();

        // delete sub-folders
        if (subfolders.Count() != 0)
        {
            foreach (var subfolder in subfolders)
            {
                // delete sub-folder files
                var subfiles = repo.GetFiles(subfolder.folder_id).ToList();
                if (subfiles.Count() != 0)
                {
                    foreach (var file in subfiles)
                    {
                        repo.DeleteFile(file.file_id);
                        System.IO.File.Delete(Server.MapPath("/content/upload/" + file.file_name));
                    }
                }
                repo.DeleteFolder(subfolder.folder_id);
            }
        }
        // delete files
        if (files.Count() != 0)
        {
            foreach (var file in files)
            {
                repo.DeleteFile(file.file_id);
                System.IO.File.Delete(Server.MapPath("/content/upload" + file.file_name));
            }
        }
        // delete the folder            
        if (folder != null)
        {
            repo.DeleteFolder(folder.folder_id);                
        }
        repo.Save();
        return new JsonResult();
    }

现在这里是FileManagerRepository

 public class FileManagerRepository
{
    private readonly iau_idahoEntities db = new iau_idahoEntities();

    public IQueryable<folders> GetParentFolders()
    {
        return db.folders.Where(f => f.parant_folder_id == 0);
    }

    public IQueryable<folders> GetSubFolders()
    {
        return db.folders.Where(f => f.parant_folder_id != 0);
    }
    public IQueryable<folders> GetSubFolders(int folder_id)
    {
        return db.folders.Where(f => f.parant_folder_id != 0 && f.parant_folder_id == folder_id);
    } 


    public IQueryable<Files> GetFiles(int id)
    {
        return db.Files.Where(f => f.folder_id == id);
    }

    public Files GetFile(int id)
    {
        return db.Files.SingleOrDefault(f => f.file_id == id);
    }

    public void UpdateDownloadCount(int id)
    {
        var file = GetFile(id);
        file.downloaded += 1;         
    }
    public void AddFolder(int parentFolderID, string folderName)
    {
        var folder = new folders { create_date = DateTime.Now, parant_folder_id = parentFolderID, folder_name = folderName };
        db.folders.AddObject(folder);
    }

    public void DeleteFolder(int folder_id)
    {
        var folder = db.folders.SingleOrDefault(f => f.folder_id == folder_id);
        db.folders.DeleteObject(folder);
    }
    public void Save()
    {
        db.SaveChanges();
    }

    public void AddFile(int folder_id,string filename, string description)
    {
        var file = new Files { 
            folder_id = folder_id, 
            file_name = filename, 
            file_extension = filename.Substring(filename.Length - 3, 3), 
            description = description,
            downloaded = 0, 
            physical_name = filename.Substring(0, filename.Length - 4), 
            upload_date = DateTime.Now 
        };
        db.Files.AddObject(file);            
    }

    internal void DeleteFile(int fileID)
    {
        var fileToDelete = db.Files.SingleOrDefault(file => file.file_id == fileID);
        db.Files.DeleteObject(fileToDelete);
    }

    internal folders GetFolder(int folderID)
    {
        return db.folders.SingleOrDefault(folder => folder.folder_id == folderID);
    }
}

问题是我一直收到以下EF异常： 已经有一个与此命令关联的开放DataReader，必须先关闭

我尝试将MultipleActiveResultSets = true添加到web.config中的连接字符串中，但我仍然得到异常。我知道为什么会抛出这个异常，但我不知道如何做我需要做的事情并防止它抛出异常。

请帮助!!!

Answer 1

将var subfolders = repo.GetSubFolders(folderID);行更改为var subfolders = repo.GetSubFolders(folderID).ToList();

Answer 2

如果我将对存储库的所有后续调用更改为ToList（），则所有调用都应该如此。

    var folder     = repo.GetFolder(folderID);
    var subfolders = repo.GetSubFolders(folderID).ToList();
    var files      = repo.GetFiles(folderID).ToList();

    // delete sub-folders
    if (subfolders.Count() != 0)
    {
        foreach (var subfolder in subfolders)
        {
            // delete sub-folder files
            var subfiles = repo.GetFiles(subfolder.folder_id).ToList();

迭代集合时的实体框架异常

2 个答案: