花了很长时间后突然发生SqlConnection.open（）错误

Question

我用sqlserver2008和c＃winform（直接连接）创建了一个程序。

当我首先启动程序时，它运行良好，连接没有问题。 但是在没有使用该程序几个小时或几天（无法确切检查）之后，Sqlconnection.open（）突然抛出一个异常。 我猜这与连接池或其他东西有关，但我没能在谷歌或这里搜索。

以下是我的错误消息和连接代码。

ERROR: (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error:) An error has occurred while establishing a connection to the server. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)


location: System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling)      location: System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)      location: System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)      location: System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)      location: System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)      location: System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)      location: System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)     location: System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)      location: System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)      location: System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)      location: System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)      location: System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)      location: System.Data.SqlClient.SqlConnection.Open()      location: DHP_QRChecker.Module.clsDBMgr.Open(String query)

代码：

class clsDBMgr
    {
        private SqlConnection conn;
        private string strConn = "";

        //prepare connection string
        public clsDBMgr()
        {
            strConn = "server=" + Constants.g_strDB_Addr + ";database=" + Constants.g_strDB_Name
                + ";User ID=" + Constants.g_strDB_ID + ";Password=" + Constants.g_strDB_PW;
        }

        //try open once and close
        //create and return SqlCommand object
        public SqlCommand Open(string query)
        {
            SqlCommand cmd = null;

            try
            {
                conn = new SqlConnection(strConn);
                cmd = new SqlCommand(query, conn);              
                **conn.Open(); //error occurs suddenly**
            }
            catch (Exception _error)
            {
                clsFunc.MsgErr(_error.Message, _error);
                return null;
            }
            finally
            {
                Close();
            }

            return cmd;
        }  

        //execute query.
        //at finally block, always call SqlConnection.Close();
        public DataRow[] Execute(string query)
        {
            SqlCommand cmd = null;
            DataRow[] row = null;

            try
            {      
                cmd = Open(query);                
                cmd.CommandTimeout = 0;
                if (cmd == null)
                    throw new Exception("can't connect to db.");


                SqlDataAdapter adpt = new SqlDataAdapter(cmd);
                DataSet ds = new DataSet();
                adpt.Fill(ds);

                if (ds == null || ds.Tables.Count == 0)
                    throw new Exception("can't fill");

                DataTable dt = ds.Tables[ds.Tables.Count - 1];
                row = dt.Select();

                if (!IsValid(row))
                    throw new Exception("데이터베이스 정보가 유효하지 않습니다.");
            }
            catch (Exception _error)
            {
                string errorMsg;

                errorMsg = _error.Message;

                clsFunc.MsgErr(errorMsg, _error);
                row = null;

            }
            finally
            {
                Close();
            }

            return row;
        }

        //Close function
        public void Close()
        {
            if (conn != null)
                conn.Close();
        }

        private bool IsValid(DataRow row)
        {
            if (row == null || row.ItemArray.Length == 0 || row[0] == null)
                return false;
            else
                return true;
        }

}