asp.net+Sqlite 时不时出现Unable to open the database file

Question

网站是能运行的起来，只不过时不时的会出现下面这个错误，没有规律的。app_data已经加了everyone写入权限了。
=================
Unable to open the database file 
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.Data.SQLite.SQLiteException: Unable to open the database file源错误: 
行 162:    {
行 163:        if (connection.State != ConnectionState.Open)
行 164:            connection.Open();
行 165:    }
行 166:===============================
下面是我的类部份方法，也以及及时的关闭了数据库连接。大家帮忙看看哪里还需要改进的。谢谢
[code=C#]
public class SQLiteHelper
{
    public SQLiteHelper()
    {    }
    //数据库连接字符串(web.config来配置)，可以动态更改SQLString支持多数据库.         
    public static string connectionString = "Data Source=" + System.Web.HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["ConnectionSQLite"]) + ";Version=3;";    public static SQLiteParameter GetOleDbParameter(string paraName, DbType type, int paraSize, Object value)
    {
        SQLiteParameter para = new SQLiteParameter(paraName, type, paraSize);
        para.Value = value;
        return para;
    }
    public static string GetTableData(string Fields, string ID)
    {
        string Sql = "select " + Fields + " From [table] where id='" + ID + "'";
        return GetData(Sql);
    }    public static string GetData(string Sql)
    {
        object obj = GetSingle(Sql);
        if (obj == null)
        {
            return "";
        }
        return obj.ToString();
    }    public static int GetMaxID(string FieldName, string TableName)
    {
        string strsql = "select max(" + FieldName + ")+1 from " + TableName;
        object obj = GetSingle(strsql);
        if (obj == null)
        {
            return 1;
        }
        else
        {
            return int.Parse(obj.ToString());
        }
    }    public static bool Exists(string strSql)
    {
        object obj = GetSingle(strSql);
        int cmdresult;
        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
        {
            cmdresult = 0;
        }
        else
        {
            cmdresult = int.Parse(obj.ToString());
        }
        if (cmdresult == 0)
        {
            return false;
        }
        else
        {
            return true;
        }
    }    public static bool Exists(string strSql, params SQLiteParameter[] cmdParms)
    {
        object obj = GetSingle(strSql, cmdParms);
        int cmdresult;
        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
        {
            cmdresult = 0;
        }
        else
        {
            cmdresult = int.Parse(obj.ToString());
        }
        if (cmdresult == 0)
        {
            return false;
        }
        else
        {
            return true;
        }
    }    #endregion    /// <summary>
    /// 保证数据库连接处于打开状态
    /// </summary>
    /// <param name="connection"></param>
    public static void OpenDb(SQLiteConnection connection)
    {
        if (connection.State != ConnectionState.Open)
            connection.Open();
    }    public static int ExecuteSql(string SQLString)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            using (SQLiteCommand cmd = new SQLiteCommand(SQLString, connection))
            {
                OpenDb(connection);
                try
                {
                    int rows = cmd.ExecuteNonQuery();
                    return rows;
                }
                catch (System.Data.SQLite.SQLiteException E)
                {
                    throw new Exception(E.Message);
                }
            }
        }
    }   public static int ExecuteSql(string SQLString, string content)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            SQLiteCommand cmd = new SQLiteCommand(SQLString, connection);
            using (cmd)
            {
                SQLiteParameter myParameter = new SQLiteParameter("@content", DbType.String);
                myParameter.Value = content;
                cmd.Parameters.Add(myParameter);
                try
                {
                    if (connection.State != ConnectionState.Open)
                        connection.Open();
                    int rows = cmd.ExecuteNonQuery();
                    return rows;
                }
                catch (System.Data.SQLite.SQLiteException E)
                {
                    throw new Exception(E.Message);
                }
                finally
                {
                    cmd.Dispose();
                    connection.Close();
                }
            }
        }
    }

Answer 1

接着楼上的： public static object ExecuteSqlGet(string SQLString, string content)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            using (SQLiteCommand cmd = new SQLiteCommand(SQLString, connection))
            {
                SQLiteParameter myParameter = new SQLiteParameter("@content", DbType.String);
                myParameter.Value = content;
                cmd.Parameters.Add(myParameter);
                try
                {
                    if (connection.State != ConnectionState.Open)
                        connection.Open();
                    object obj = cmd.ExecuteScalar();
                    if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                    {
                        return null;
                    }
                    else
                    {
                        return obj;
                    }
                }
                catch (System.Data.SQLite.SQLiteException E)
                {
                    throw new Exception(E.Message);
                }
                finally
                {
                    cmd.Dispose();
                    connection.Close();
                }
            }
        }
    }    public static int ExecuteSqlInsertImg(string strSQL, byte[] fs)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            using (SQLiteCommand cmd = new SQLiteCommand(strSQL, connection))
            {
                SQLiteParameter myParameter = new SQLiteParameter("@fs", DbType.Binary);
                myParameter.Value = fs;
                cmd.Parameters.Add(myParameter);
                try
                {
                    if (connection.State != ConnectionState.Open)
                        connection.Open();
                    int rows = cmd.ExecuteNonQuery();
                    return rows;
                }
                catch (System.Data.SQLite.SQLiteException E)
                {
                    throw new Exception(E.Message);
                }
                finally
                {
                    cmd.Dispose();
                    connection.Close();
                }
            }
        }
    }    public static object GetSingle(string SQLString)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            using (SQLiteCommand cmd = new SQLiteCommand(SQLString, connection))
            {
                try
                {
                    object obj = cmd.ExecuteScalar();
                    if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                    {
                        return null;
                    }
                    else
                    {
                        return obj;
                    }
                }
                catch (System.Data.SQLite.SQLiteException e)
                {
                    //connection.Close();
                    throw new Exception(e.Message);
                }
                finally
                {
                    connection.Close();
                    cmd.Dispose();
                }
            }
        }
    }    public static DataSet Query(string SQLString)
    {        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            try
            {
                DataSet ds = new DataSet();
                using (SQLiteDataAdapter command = new SQLiteDataAdapter(SQLString, connection))
                {
                    command.Fill(ds, "ds");
                }
                return ds;
            }
            catch (System.Data.SQLite.SQLiteException ex)
            {
                throw new Exception(ex.Message);
            }
        }    }    public static DataSet Query(string SQLString, string TableName)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            DataSet ds = new DataSet();
            try
            {
                SQLiteDataAdapter command = new SQLiteDataAdapter(SQLString, connection);
                using (command)
                {
                    command.Fill(ds, TableName);
                }
            }
            catch (System.Data.SQLite.SQLiteException ex)
            {
                throw new Exception(ex.Message);
            }
            return ds;
        }
    }
    public static DataSet Query(string SQLString, int Times)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            DataSet ds = new DataSet();
            try
            {
                SQLiteDataAdapter command = new SQLiteDataAdapter(SQLString, connection);
                using (command)
                {
                    command.SelectCommand.CommandTimeout = Times;
                    command.Fill(ds, "ds");
                }
                return ds;
            }
            catch (System.Data.SQLite.SQLiteException ex)
            {
                throw new Exception(ex.Message);
            }
        }
    }    public static int ExecuteSql(string SQLString, params SQLiteParameter[] cmdParms)
    {
        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
        {
            OpenDb(connection);
            using (SQLiteCommand cmd = new SQLiteCommand())
            {
                try
                {
                    PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                    int rows = cmd.ExecuteNonQuery();
                    cmd.Parameters.Clear();
                    return rows;
                }
                catch (System.Data.SQLite.SQLiteException E)
                {
                    throw new Exception(E.Message);
                }
            }
        }
    }

Answer 2

sqllite 不支持多个线程同时写入，对于b/s，不应该使用

Answer 3

多人同时向sqlite插入数据的话，容易出错？

Answer 4

刚找到一篇文章：
SQLite省略了一些人们认为比较有用的特性, 例如高并发性、 严格的存取控制、 丰富的内置功能、 存储过程、复杂的SQL语言特性、 
SQLite最佳试用场合    网站
嵌入式设备和应用软件
应用程序文件格式
。。
估计是我上面的操作类写的不够严谨。

Answer 5

那些代码都是操作数据库的。就是普通的读取到DataSet,DataTable 执行SQL语句之类的

Answer 6

我也遇到了同样的问题，终于解决了connectionstring里面要加上";Pooling=True",sqllite默认没有打开连接池。要指定。

Answer 7

谢谢sweatypalms，我的连接代码改成如下：
<add key="ConnectionSQLite" value="App_Data/test.db3"/>Data Source=" + System.Web.HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["ConnectionSQLite"]) + ";Version=3;Pooling=True;
===============
不知跟你的是否一样，能贴出你的代码吗？你现在还有出现这错误么？

Answer 8

只要换成mysql就可以解决了。

Answer 9

现在数据库已经是采用Sqlite了，换mysql是不可能了。

Answer 10

using (SQLiteConnection connection = new SQLiteConnection(connectionString))
   {
   OpenDb(connection);
   SQLiteCommand cmd = new SQLiteCommand(SQLString, connection);
   using (cmd)
   {
   SQLiteParameter myParameter = new SQLiteParameter("@content", DbType.String);
   myParameter.Value = content;
   cmd.Parameters.Add(myParameter);
   try
   {
   if (connection.State != ConnectionState.Open)
   connection.Open();
   int rows = cmd.ExecuteNonQuery();
   return rows;
   }
   catch (System.Data.SQLite.SQLiteException E)
   {
   throw new Exception(E.Message);
   }
   finally
   {
   cmd.Dispose();
   connection.Close();
   }
   }
 这样的代码有问题，using 相当于 try finally,这样的话finally里面很可能报异常，但应该不影响数据库

Answer 11

不允许多线程访问，2楼正解。我就是这样解决的：http://duan.es