Category Archives: OS

最近项目中用了COM控件，同时也用了多线程，在等待线程退出的地方，使用了

AutoResetEvent[] tEevents;
//...
WaitHandle.WaitAll(tEevents);

程序运行到这里，就会报错：

不支持一个STA线程上针对多个句柄的WaitAll

当时事情很急，将其调整为

AutoResetEvent[] tEevents;
//...
foreach(var tEvent in tEevents)
{
    tEvent.WaitOne();
}

就将这个问题绕了过去。

后来，在Stackoverflow上面，查了STA和MTA的区别。COM线程模型称为Apartment模型，分为STA和MTA两种。
STA（Single Thread Apartment）：
STA是非线程安全的，常用于UI界面，其他线程要访问STA模式的COM组件，需要通过STA线程进行访问（其实就变成了单线程调用）
MTA（Multi Thread Apartment）：
MTA是线程安全的，COM的程序员自己处理了并发的问题，其他线程可以直接访问COM组件

参考资料：
Could you explain STA and MTA?

        //Form程序
        private static String getExeFileFolder()
        {
            String strExeFolder = System.Reflection.Assembly.GetExecutingAssembly().Location;
            int nPos = strExeFolder.LastIndexOf("\\");
            if (nPos >= 0)
            {
                strExeFolder = strExeFolder.Substring(0, nPos + 1);
            }
            else
            {
                strExeFolder = strExeFolder + "\\";
            }

            return strExeFolder;
        }

        //IIS程序
        String rootPath = Request.PhysicalApplicationPath;
        String strExeFolder = getExeFileFolder(rootPath);
        private static String getExeFileFolder(String strExeFolder)
        {
            int nPos = strExeFolder.LastIndexOf("\\");
            if (nPos >= 0)
            {
                strExeFolder = strExeFolder.Substring(0, nPos + 1);
            }
            else
            {
                strExeFolder = strExeFolder + "\\";
            }

            return strExeFolder;
        }

        int nMaxThreadNum = 5;
        List<List<JobParam>> jobQueue = new List<List<JobParam>>();
        //...
        for (int i = 0; i < nMaxThreadNum;i++)
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(AsyncDoRetrieve), jobQueue&#91;i&#93;);
        }

        static void AsyncDoRetrieve(object state)
        {
            if (!(state == null && state is List<JobParam>)) return;
            List<JobParam> jobParams= state as List<JobParam> ;
            foreach(JobParam param in jobParams)
            {
                param.delegateDoSomeThing.BeginInvoke(param,null,null);
            }
        }

1.IDBHelper.cs

    interface IDBHelper
    {
        void initDB();
        void closeDB();
        void ExecSQL(String execSql);
        DataTable ExecQuery(String querySql);
    }

2.ZDBHelperSQLLite.cs

    class ZDBHelperSQLLite : IDBHelper
    {
        String dataSource = "";
        SQLiteConnection connection = null;
        public void initDB(String dbPath)
        {
            dataSource = "Data Source =" + dbPath();
            connection = new SQLiteConnection(dbFile);
            connection.Open();
            initTables();
            CreateFileInfoTable();
        }
        
        public void closeDB()
        {
            connection.Close();
        }

        private void initTables()
        {
            String sqlCreate01 = "CREATE TABLE IF NOT EXISTS visitlog(user_id varchar(64), visit_path varchar(256), visit_time integer);";
            SQLiteCommand cmdCreateTable = new SQLiteCommand(connection);
            cmdCreateTable.CommandText = sqlCreate01;
            cmdCreateTable.ExecuteNonQuery();
        }
  
        public void ExecSQL(String execSql)
        {
            SQLiteTransaction transaction = connection.BeginTransaction();
            SQLiteCommand cmdExec = new SQLiteCommand(execSql, connection, transaction );
            cmdExec.ExecuteNonQuery();
            transaction.Commit();
        }

        public DataTable ExecQuery(String querySql)
        {
            SQLiteCommand cmdQuery = new SQLiteCommand(querySql, connection);
            SQLiteDataReader reader = cmdQuery.ExecuteReader();

            DataTable datatable = new DataTable();
            DataTable schemaTable = reader.GetSchemaTable();
            foreach (DataRow myRow in schemaTable.Rows)
            {
                DataColumn myDataColumn = new DataColumn();
                myDataColumn.DataType = myRow.GetType();
                myDataColumn.ColumnName = myRow[0].ToString();
                datatable.Columns.Add(myDataColumn);
            }
            schemaTable = null;

            while (reader.Read())
            {
                DataRow myDataRow = datatable.NewRow();
                for (int i = 0; i < reader.FieldCount; i++)
                {
                    myDataRow[i] = reader[i].ToString();
                }
                datatable.Rows.Add(myDataRow);
                myDataRow = null;
            }
            reader.Close();

            return datatable;
        }
    }