C#代码的数据库打开关闭问题

Question

public class DbHelperOleDb
    {
        private string connectionString = string.Empty;
        public DbHelperOleDb(string conn)
        {
            connectionString = conn;
        }        #region  执行简单SQL语句        /// <summary>
        /// 执行SQL语句，返回影响的记录数
        /// </summary>
        /// <param name="SQLString">SQL语句</param>
        /// <returns>影响的记录数</returns>
        public int ExecuteSql(string SQLString)
        {
            using (OleDbConnection connection = new OleDbConnection(connectionString))
            {
                using (OleDbCommand cmd = new OleDbCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        int rows = cmd.ExecuteNonQuery();
                        return rows;
                    }
                    catch (System.Data.OleDb.OleDbException E)
                    {
                        connection.Close();
                        throw new Exception(E.Message);
                    }
                }
            }
        }        #endregion
}请问上述的C#代码，使用using方式来打开数据库，虽然可以用完后扔掉资源，我的问题是：ExecuteSql执行完了之后会保证关闭打开的数据库吗？（不出现异常的情况下），谢谢各位大神，本人这两天开始接触C#

Answer 1

using(var connection = new Connection())
{
    connection.Open();
}相当于try
{
    var connection = new Connection();
    connection.Open();
}
finally
{
    connection.Close();
}

Answer 2

可以关闭打开的连接.因为Using会调用OleDbConnection的IDispot接口.catch(System.Data.OleDb.OleDbException E)
{
       connection.Close();//这是一条无意义的代码
       throw new Exception(E.Message);
}

Answer 3

using里面的try catch都毫无意义(对于你的异常捕获没有任何特殊处理情况下)

Answer 4

在异常处理后面加个finally{  connection.Close();    }     ；把关闭数据库放在这个里面就可以了，不管程序是正常执行，还是出现异常处理，都会执行这条语句。

Answer 5

Code Original:
//连接数据库的字符串.
            string strConn = ConfigurationManager.ConnectionStrings["ADONetTest.Properties.Settings.DBTestConnectionString"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(strConn)) {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand()) {
                    cmd.CommandText = "Insert into T_Persons(FName) values('King')";
                    cmd.ExecuteNonQuery();
                    MessageBox.Show("Done!");
                }
            }
Reflector Code:
bool flag;
            string strConn = ConfigurationManager.ConnectionStrings["ADONetTest.Properties.Settings.DBTestConnectionString"].ConnectionString;
            SqlConnection conn = new SqlConnection(strConn);
            try {
                conn.Open();
                SqlCommand cmd = conn.CreateCommand();
                try {
                    cmd.CommandText = "Insert into T_Persons(FName) values('King')";
                    cmd.ExecuteNonQuery();
                    MessageBox.Show("Done!");
                }
                finally {
                    flag = cmd == null;
                    if (!flag) {
                        ((IDisposable)cmd).Dispose();
                    }
                }
            }
            finally {
                flag = conn == null;
                if (!flag) {
                    ((IDisposable)conn).Dispose();
                }
            }
这个微软还是会想到了,放心吧...两层的Try catch...