使用C＃连接到Mysql数据库 – 需要一些数据集

编辑

我显然不明白如何做到这一点。 在提供示例之后，我决定更多地阅读书籍，并尝试使用给出的示例来解决它。

谢谢。

编辑结束

我想连接到mySql DB，读取表/行，然后将它们写入控制台。 这段代码是否正确？ 我在Visual Studio 2005中得到数据集错误。

代码不是我的，从网上得到它。 我只是修改了一下（变量名等）。

如果您有一个很好的教程，请发布链接。 =）

/* Performing a SELECT statement using ADO.NET */ #region Using directives using System; using System.Data; using System.Data.SqlClient; using MySql.Data.MySqlClient; #endregion namespace testConnect1 { class SqlTest1 { static void Main() { string connectionString = "server = localhost user id = root Password = blank database = test1"; //connection string SqlConnection mySqlConnection = new SqlConnection(connectionString); //creates connection string selectString = "Select field01, field02, field03 " + "FROM myDataTable"; //selects fields to be accessed SqlCommand mySqlCommand = mySqlConnection.CreateCommand(); mySqlCommand.CommandText = selectString; SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(); mySqlDataAdapter.SelectCommand = mySqlCommand; DataSet test1DataSet = new DataSet(); //creates data set mySqlConnection.Open(); // opens connection Console.WriteLine("Retrieving rows from the test table"); string dataTableName = "myDataTable"; mySqlDataAdapter.Fill(test1DataSet, dataTableName); DataTable myDataTable = test1DataSet.Tables[myDataTable]; //i get an error here foreach (DataRow myDataRow in myDataTable.Rows) //iterates over rows in table { //Console.WriteLine("Field01") = + myDataRow[("field01")]; // i had to comment out this region because also get an error, but this is not my doubt right now //Console.WriteLine("Field02") = + myDataRow[("field02")]; //Console.WriteLine("Field03") = + myDataRow[("field03")]; } mySqlConnection.Close(); //close connection } } } 

Answer 1

这是一个简单的例子，您应该遵循以纠正方法中的错误：

SQL的东西

 drop table if exists users; create table users ( user_id int unsigned not null auto_increment primary key, username varbinary(32) unique not null ) engine=innodb; insert into users (username) values ('f00'),('bar'); 

C＃DataAdapter方法

注意我没有显式打开数据库连接 – DataAdpater为我做了这个。

 using System; using System.Collections.Generic; using System.Linq; using System.Text; // addded these using MySql.Data; using MySql.Data.MySqlClient; using System.Data; namespace mysql { class Program { static void Main(string[] args) { const string DB_CONN_STR = "Server=127.0.0.1;Uid=foo_dbo;Pwd=pass;Database=foo_db;"; MySqlConnection cn = new MySqlConnection(DB_CONN_STR); try { string sqlCmd = "select * from users order by user_id"; MySqlDataAdapter adr = new MySqlDataAdapter(sqlCmd, cn); adr.SelectCommand.CommandType = CommandType.Text; DataTable dt = new DataTable(); adr.Fill(dt); //opens and closes the DB connection automatically !! (fetches from pool) foreach (DataRow dr in dt.Rows){ Console.WriteLine(string.Format("user_id = {0}", dr["user_id"].ToString())); } } catch (Exception ex) { Console.WriteLine("{oops - {0}", ex.Message); } finally { cn.Dispose(); // return connection to pool } Console.WriteLine("press any key..."); Console.ReadKey(); } } } 

C＃DataReader示例

 using System; using System.Collections.Generic; using System.Linq; using System.Text; // addded these using MySql.Data; using MySql.Data.MySqlClient; using System.Data; namespace mysql { class Program { static void Main(string[] args) { const string DB_CONN_STR = "Server=127.0.0.1;Uid=foo_dbo;Pwd=pass;Database=foo_db;"; MySqlConnection cn = new MySqlConnection(DB_CONN_STR); try { string sqlCmd = "select * from users order by user_id"; cn.Open(); // have to explicitly open connection (fetches from pool) MySqlCommand cmd = new MySqlCommand(sqlCmd, cn); cmd.CommandType = CommandType.Text; MySqlDataReader rdr = cmd.ExecuteReader(); while (rdr.Read()){ Console.WriteLine(string.Format("user_id = {0}", rdr["user_id"].ToString())); } } catch (Exception ex) { Console.WriteLine("{oops - {0}", ex.Message); } finally { cn.Dispose(); // return connection to the pool } Console.WriteLine("press any key..."); Console.ReadKey(); } } }