C#填充datatable的两种方法

数据库的连接

/// 

    /// 连接或断开数据库的全局变量
    /// 
    MySqlConnection connection = null;
    MySqlConnectionStringBuilder conn_string = null;
    /// 

    /// 连接阅卷系统的数据库
    /// 
    /// 
    public void ConnectionDB()
    {
        conn_string = new MySqlConnectionStringBuilder();
        conn_string.Database = "数据库名称";
        conn_string.Server = "ip地址";
        conn_string.Port = 端口号;
        conn_string.UserID = "用户id";
        conn_string.Password = "密码";
        conn_string.ConnectionTimeout = 200;//超时时间
        conn_string.ConnectionLifeTime = 200;
        connection = new MySqlConnection(conn_string.ToString());
        connection.Open();
    }

    /// 

    /// 关闭数据库
    /// 
    public void CloseConn()
    {
        connection.Dispose();
        connection.Close();
    }

1.使用fill

public DataTable ExportToDataTable(string sql)  //返回DataSet对象
    {
		ConnectionDB();
        DataTable dt = new DataTable();
        MySqlDataAdapter da = new MySqlDataAdapter(sql, connection);
        da.Fill(dt);
	}

2.不使用fill

public DataTable ExportToDataTable(string sql)  //返回DataSet对象
   {
			ConnectionDB();
            DataTable dt = new DataTable();
            MySqlCommand cmd = new MySqlCommand(sql, connection);
            cmd.CommandTimeout = 200;
            MySqlDataReader reader = cmd.ExecuteReader();
            if(reader.HasRows)
            {
                int fieldCount = reader.FieldCount;
                for(int i=0; i < fieldCount; i++)
                {
                    dt.Columns.Add(reader.GetName(i), reader.GetFieldType(i));
                }
                dt.BeginLoadData();
                object[] objValues = new object[fieldCount];
                while (reader.Read())
                {
                    reader.GetValues(objValues);
                    dt.LoadDataRow(objValues, true);
                   // dt.Load(reader);
                }
                reader.Close();
                dt.EndLoadData();
                return dt;
         }
   }