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FileSystemProviderBase Class

Serves as the base class for providers that perform operations with the file system.

Namespace: DevExpress.Web

Assembly: DevExpress.Web.v18.2.dll

Declaration

public abstract class FileSystemProviderBase
Public MustInherit Class FileSystemProviderBase

Remarks

The FileSystemProviderBase class is the base class that implements the common file system provider functionality.

This class can be used as an ancestor of your custom file system provider. In this case, you should provide the implementation of the class's methods. To learn more, see the Custom File System Provider topic.

Examples

using DevExpress.Web.ASPxFileManager;
using System.IO;
public class LinqFileSystemProvider : FileSystemProviderBase {
    const int DbRootItemId = 1;
    DbFileSystemDataContext dataContext;
    Dictionary<int, DbFileSystemItem> folderCache;
    string rootFolderDisplayName;

    public LinqFileSystemProvider(string rootFolder)
        : base(rootFolder) {
        this.dataContext = new DbFileSystemDataContext();
        RefreshFolderCache();
    }

    public DbFileSystemDataContext DataContext { get { return dataContext; } }

    // Used to decrease the number of recursive LINQ to SQL queries made to a database
    public Dictionary<int, DbFileSystemItem> FolderCache { get { return folderCache; } }


    public override string RootFolderDisplayName { get { return rootFolderDisplayName; } }

    public override IEnumerable<FileManagerFile> GetFiles(FileManagerFolder folder) {
        DbFileSystemItem dbFolderItem = FindDbFolderItem(folder);
        return
            from dbItem in DataContext.DbFileSystemItems
            where !dbItem.IsFolder && dbItem.ParentId == dbFolderItem.Id
            select new FileManagerFile(this, folder, dbItem.Name);
    }
    public override IEnumerable<FileManagerFolder> GetFolders(FileManagerFolder parentFolder) {
        DbFileSystemItem dbFolderItem = FindDbFolderItem(parentFolder);
        return
            from dbItem in FolderCache.Values
            where dbItem.IsFolder && dbItem.ParentId == dbFolderItem.Id
            select new FileManagerFolder(this, parentFolder, dbItem.Name);
    }
    public override bool Exists(FileManagerFile file) {
        return FindDbFileItem(file) != null;
    }
    public override bool Exists(FileManagerFolder folder) {
        return FindDbFolderItem(folder) != null;
    }
    public override System.IO.Stream ReadFile(FileManagerFile file) {
        return new MemoryStream(FindDbFileItem(file).Data.ToArray());
    }
    public override DateTime GetLastWriteTime(FileManagerFile file) {
        var dbFileItem = FindDbFileItem(file);
        return dbFileItem.LastWriteTime.GetValueOrDefault(DateTime.Now);
    }

    // File/folder management operations
    public override void CreateFolder(FileManagerFolder parent, string name) {
        UpdateAndSubmitChanges(parent,
            dbItem => DataContext.DbFileSystemItems.InsertOnSubmit(new DbFileSystemItem() {
                IsFolder = true,
                LastWriteTime = DateTime.Now,
                Name = name,
                ParentId = dbItem.Id
            }));
    }
    public override void DeleteFile(FileManagerFile file) {
        UpdateAndSubmitChanges(file, dbItem =>
DataContext.DbFileSystemItems.DeleteOnSubmit(dbItem));
    }
    public override void DeleteFolder(FileManagerFolder folder) {
        UpdateAndSubmitChanges(folder, dbItem =>
DataContext.DbFileSystemItems.DeleteOnSubmit(dbItem));
    }
    public override void MoveFile(FileManagerFile file, FileManagerFolder newParentFolder) {
        UpdateAndSubmitChanges(file, dbItem => dbItem.ParentId =
FindDbFolderItem(newParentFolder).Id);
    }
    public override void MoveFolder(FileManagerFolder folder, FileManagerFolder newParentFolder)
{
        UpdateAndSubmitChanges(folder, dbItem => dbItem.ParentId =
FindDbFolderItem(newParentFolder).Id);
    }
    public override void RenameFile(FileManagerFile file, string name) {
        UpdateAndSubmitChanges(file, dbItem => dbItem.Name = name);
    }
    public override void RenameFolder(FileManagerFolder folder, string name) {
        UpdateAndSubmitChanges(folder, dbItem => dbItem.Name = name);
    }
    public override void UploadFile(FileManagerFolder folder, string fileName, Stream content) {
        UpdateAndSubmitChanges(folder,
            dbItem => DataContext.DbFileSystemItems.InsertOnSubmit(new DbFileSystemItem() {
                Name = fileName,
                Data = ReadAllBytes(content),
                ParentId = dbItem.Id,
                LastWriteTime = DateTime.Now,
                IsFolder = false
            }));
    }

    protected void UpdateAndSubmitChanges(FileManagerFile file, Action<DbFileSystemItem> update)
{
        UpdateAndSubmitChangesCore(FindDbFileItem(file), update);
    }
    protected void UpdateAndSubmitChanges(FileManagerFolder folder, Action<DbFileSystemItem>
update) {
        UpdateAndSubmitChangesCore(FindDbFolderItem(folder), update);
    }
    protected void UpdateAndSubmitChangesCore(DbFileSystemItem dbitem, Action<DbFileSystemItem>
update) {
        update(dbitem);
        DataContext.SubmitChanges();
        RefreshFolderCache();
    }
    protected DbFileSystemItem FindDbFileItem(FileManagerFile file) {
        DbFileSystemItem dbFolderItem = FindDbFolderItem(file.Folder);
        if(dbFolderItem == null)
            return null;
        return
            (from dbItem in DataContext.DbFileSystemItems
             where dbItem.ParentId == dbFolderItem.Id && !dbItem.IsFolder && dbItem.Name ==
file.Name
             select dbItem).FirstOrDefault();
    }
    protected DbFileSystemItem FindDbFolderItem(FileManagerFolder folder) {
        return
            (from dbItem in FolderCache.Values
             where dbItem.IsFolder && GetRelativeName(dbItem) == folder.RelativeName
             select dbItem).FirstOrDefault();
    }

    // Returns the path to a specified folder relative to a root folder
    protected string GetRelativeName(DbFileSystemItem dbFolder) {
        if(dbFolder.Id == DbRootItemId) return string.Empty;
        if(dbFolder.ParentId == DbRootItemId) return dbFolder.Name;
        if(!FolderCache.ContainsKey(dbFolder.ParentId)) return null;
        string name = GetRelativeName(FolderCache[dbFolder.ParentId]);
        return name == null ? null : Path.Combine(name, dbFolder.Name);
    }

    // Caches folder names in memory and obtains a root folder's name
    protected void RefreshFolderCache() {
        this.folderCache = (
            from dbItem in DataContext.DbFileSystemItems
            where dbItem.IsFolder
            select dbItem
        ).ToDictionary(i => i.Id);

        this.rootFolderDisplayName = (
            from dbItem in FolderCache.Values
            where dbItem.Id == DbRootItemId
            select dbItem.Name).First();
    }
    protected static byte[] ReadAllBytes(Stream stream) {
        byte[] buffer = new byte[16 * 1024];
        int readCount;
        using(MemoryStream ms = new MemoryStream()) {
            while((readCount = stream.Read(buffer, 0, buffer.Length)) > 0) {
                ms.Write(buffer, 0, readCount);
            }
            return ms.ToArray();
        }
    }
}
See Also