A simple wrapper to GridFS in mongodb for CRUD functionality on files.

ConnectionInformation.cs

/// <summary>
/// Singleton for MongoDB connection (just a sample - for an idea)
/// </summary>
public class ConnectionInformation
{
  #region fields

  private static ConnectionInformation instance;
  private static object syncLock = new object();

  #endregion
  
  #region public properties

  public static ConnectionInformation Instance
  {
      get 
      {
          if (instance == null)
          {
              lock (syncLock)
              {
                  if (instance == null)
                  {
                      instance = new ConnectionInformation();
                  }
              }
          }

          return instance;
      }
  }
  
  public MongoDatabase Database
  {
    get
    {
      return database;
    }
  }

  #endregion
}

MongoFileSystem.cs

using MongoDB.Driver;
using MongoDB.Driver.Builders;
using MongoDB.Driver.GridFS;
using System;
using System.IO;

public class MongoFileSystem
{
  ///<summary>
  /// checks if a file exists with the given path.
  ///</summary>
  public bool Exists(string path)
  {
      if (string.IsNullOrEmpty(path))
      {
          throw new ArgumentNullException("path");
      }
      IMongoQuery query = Query.EQ("filename", path);
      MongoGridFSFileInfo file = ConnectionInformation.Instance.Database.GridFS.FindOne(query);
      return (file != null);
  }
  
  ///<summary>
  /// returns Stream to the file with given path. returns null
  /// if the file does not exist.
  ///</summary>
  public Stream GetFile(string path)
  {
      if (string.IsNullOrEmpty(path))
      {
          throw new ArgumentNullException("path");
      }

      IMongoQuery query = Query.EQ("filename", path);
      MongoGridFSFileInfo file = ConnectionInformation.Instance.Database.GridFS.FindOne(query);

      Stream stream = null;

      if (file != null)
      {
          stream = file.OpenRead();
      }

      return stream;
  }
  
  /// <summary>
  /// saves a file in the given path. if the file already exists
  /// in the path, throws exception.
  /// </summary>
  public void Save(string path, string filename)
  {
      if (string.IsNullOrEmpty(path))
      {
          throw new ArgumentNullException("path");
      }

      if (string.IsNullOrEmpty(filename))
      {
          throw new ArgumentNullException("filename");
      }

      if (!File.Exists(filename))
      {
          throw new ArgumentException("filename");
      }

      MongoGridFSFileInfo gridFsInfo = ConnectionInformation.Instance.Database.GridFS.Upload(filename, path);
  }

  /// <summary>
  /// deletes the file in the given path.
  /// </summary>
  public void Delete(string path)
  {
      if (string.IsNullOrEmpty(path))
      {
          throw new ArgumentNullException("path");
      }

      ConnectionInformation.Instance.Database.GridFS.Delete(path);
  }
}