using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SQLite;
using System.Threading;
using System.Data;
namespace DataAccess
{
/////////////////
public sealed class SqliteConn
{
  private bool m_disposed;
  private static Dictionary<String, SQLiteConnection> connPool =
    new Dictionary<string, SQLiteConnection>();
  private static Dictionary<String, ReaderWriterLock> rwl =
    new Dictionary<String, ReaderWriterLock>();
  private static readonly SqliteConn instance = new SqliteConn();
  private static string DEFAULT_NAME = "LOCAL";
  #region Init
  // 使用單例，解決初始化與銷毀時的問題
  private SqliteConn()
  {
    rwl.Add("LOCAL", new ReaderWriterLock());
    rwl.Add("DB1", new ReaderWriterLock());
    connPool.Add("LOCAL", CreateConn("\\local.db"));
    connPool.Add("DB1", CreateConn("\\db1.db"));
    Console.WriteLine("INIT FINISHED");
  }
  private static SQLiteConnection CreateConn(string dbName)
  {
    SQLiteConnection _conn = new SQLiteConnection();
    try
    {
      string pstr = "pwd";
      SQLiteConnectionStringBuilder connstr = new SQLiteConnectionStringBuilder();
      connstr.DataSource = Environment.CurrentDirectory + dbName;
      _conn.ConnectionString = connstr.ToString();
      _conn.SetPassword(pstr);
      _conn.Open();
      return _conn;
    }
    catch (Exception exp)
    {
      Console.WriteLine("===CONN CREATE ERR====\r\n{0}", exp.ToString());
      return null;
    }
  }
  #endregion
  #region Destory
  // 手動控制銷毀，保證數(shù)據(jù)完整性
  public void Dispose()
  {
    Dispose(true);
    GC.SuppressFinalize(this);
  }
  protected void Dispose(bool disposing)
  {
    if (!m_disposed)
    {
      if (disposing)
      {
        // Release managed resources
        Console.WriteLine("關(guān)閉本地DB連接...");
        CloseConn();
      }
      // Release unmanaged resources
      m_disposed = true;
    }
  }
  ~SqliteConn()
  {
    Dispose(false);
  }
  public void CloseConn()
  {
    foreach (KeyValuePair<string, SQLiteConnection> item in connPool)
    {
      SQLiteConnection _conn = item.Value;
      String _connName = item.Key;
      if (_conn != null && _conn.State != ConnectionState.Closed)
      {
        try
        {
          _conn.Close();
          _conn.Dispose();
          _conn = null;
          Console.WriteLine("Connection {0} Closed.", _connName);
        }
        catch (Exception exp)
        {
          Console.WriteLine("嚴(yán)重異常: 無法關(guān)閉本地DB {0} 的連接。", _connName);
          exp.ToString();
        }
        finally
        {
          _conn = null;
        }
      }
    }
  }
  #endregion
  #region GetConn
  public static SqliteConn GetInstance()
  {
    return instance;
  }
  public SQLiteConnection GetConnection(string name)
  {
    SQLiteConnection _conn = connPool[name];
    try
    {
      if (_conn != null)
      {
        Console.WriteLine("TRY GET LOCK");
        //加鎖，直到釋放前，其它線程無法得到conn
        rwl[name].AcquireWriterLock(3000);
        Console.WriteLine("LOCK GET");
        return _conn;
      }
    }
    catch (Exception exp)
    {
      Console.WriteLine("===GET CONN ERR====\r\n{0}", exp.StackTrace);
    }
    return null;
  }
  public void ReleaseConn(string name)
  {
    try
    {
      //釋放
      Console.WriteLine("RELEASE LOCK");
      rwl[name].ReleaseLock();
    }
    catch (Exception exp)
    {
      Console.WriteLine("===RELEASE CONN ERR====\r\n{0}", exp.StackTrace);
    }
  }
  public SQLiteConnection GetConnection()
  {
    return GetConnection(DEFAULT_NAME);
  }
  public void ReleaseConn()
  {
    ReleaseConn(DEFAULT_NAME);
  }
  #endregion
}
}
////////////////////////

SQLiteConnection conn = null;
try
{
  conn = SqliteConn.GetInstance().GetConnection();
  //在這里寫自己的代碼
}
finally
{
  SqliteConn.GetInstance().ReleaseConn();
}