C#--MySQL数据库基本操作（增、删、改、查）
写在前面：
常用数据库：
SQLserver：https://www.cnblogs.com/mexihq/p/11636785.html
Oracle：https://www.cnblogs.com/mexihq/p/11700741.html
MySQL：https://www.cnblogs.com/mexihq/p/12463423.html
Access：https://www.cnblogs.com/mexihq/p/12466970.html
在日常的工作中，通常一个项目会大量用的数据库的各种基本操作，因此小编几个常见的数据库的操作封装成了一个dll方便后续的开发使用。本文则主要是记录了C#对MySQL的连接、增、删、改、查的基本操作，如有什么问题还请各位大佬指教。后续也将对其他几个常用的数据库进行相应的整理。话不多说，直接开始码代码。
引用：
MySQL的引用需要去手动下载
using MySql.Data.MySqlClient; //MySQL引用集
using System.Data; //DataSet引用集
先声明一个MySqlConnection 便于后续使用。
private MySqlConnection mysql_con;
MySQL打开：
/// <summary>
/// MySQL open
/// </summary>
/// <param name="link">link statement</param>
/// <returns>Success:success; Fail:reason</returns>
public string MySQL_Open(string link)
{
try
{
mysql_con = new MySqlConnection(link);
mysql_con.Open();
return "success";
}
catch (Exception ex)
{
return ex.Message;
}
}
MySQL关闭：
/// <summary>
/// MySQL close
/// </summary>
/// <returns>Success:success Fail:reason</returns>
public string MySQL_Close()
{
try
{
if (mysql_con == null)
{
return "No database connection";
}
if (mysql_con.State == ConnectionState.Open || mysql_con.State == ConnectionState.Connecting)
{
mysql_con.Close();
mysql_con.Dispose();
}
else
{
if (mysql_con.State == ConnectionState.Closed)
{
return "success";
}
if (mysql_con.State == ConnectionState.Broken)
{
return "ConnectionState:Broken";
}
}
return "success";
}
catch (Exception ex)
{
return ex.Message;
}
}
MySQL的增删改：
/// <summary>
/// MySQL insert,delete,update
/// </summary>
/// <param name="sql">insert,delete,update statement</param>
/// <returns>Success:success + Number of affected rows; Fail:reason</returns>
public string MySQL_Insdelupd(string sql)
{
try
{
int num = 0;
if (mysql_con == null)
{
return "Please open the database connection first";
}
if (mysql_con.State == ConnectionState.Open)
{
MySqlCommand sqlCommand = new MySqlCommand(sql, mysql_con);
num = sqlCommand.ExecuteNonQuery();
}
else
{
if (mysql_con.State == ConnectionState.Closed)
{
return "Database connection closed";
}
if (mysql_con.State == ConnectionState.Broken)
{
return "Database connection is destroyed";
}
if (mysql_con.State == ConnectionState.Connecting)
{
return "The database is in connection";
}
}
return "success" + num;
}
catch (Exception ex)
{
return ex.Message.ToString();
}
}
MySQL的查：
/// <summary>
/// MySQL select
/// </summary>
/// <param name="sql">select statement</param>
/// <param name="record">Success:success; Fail:reason</param>
/// <returns>select result</returns>
public DataSet MySQL_Select(string sql, out string record)
{
try
{
//储存数据的工具初始化
DataSet dataSet = new DataSet();
if (mysql_con == null)
{
record = "Please open the database connection first";
return dataSet;
}
if (mysql_con.State == ConnectionState.Open)
{
MySqlDataAdapter sqlDataAdapter = new MySqlDataAdapter(sql, mysql_con);
sqlDataAdapter.Fill(dataSet, "sample");
sqlDataAdapter.Dispose();
record = "success";
return dataSet;
}
if (mysql_con.State == ConnectionState.Closed)
{
record = "Database connection closed";
return dataSet;
}
if (mysql_con.State == ConnectionState.Broken)
{
record = "Database connection is destroyed";
return dataSet;
}
if (mysql_con.State == ConnectionState.Connecting)
{
record = "The database is in connection";
return dataSet;
}
record = "ERROR";
return dataSet;
}
catch (Exception ex)
{
DataSet dataSet = new DataSet();
record = ex.Message.ToString();
return dataSet;
}
}
小编发现以上这种封装方式还是很麻烦，每次对MySQL进行增删改查的时候还得先打开数据库，最后还要关闭，实际运用起来比较麻烦。因此对上面两个增删改查的方法进行了重载，在每次进行操作时都先打开数据库，然后关闭数据库。
/// <summary>
/// MySQL insert,delete,update
/// </summary>
/// <param name="sql">insert,delete,update statement</param>
/// <param name="link">link statement</param>
/// <returns>Success:success + Number of affected rows; Fail:reason</returns>
public string MySQL_Insdelupd(string sql, string link)
{
try
{
int num = 0;
using (MySqlConnection con = new MySqlConnection(link))
{
con.Open();
//操作数据库的工具SqlCommand
MySqlCommand cmd = new MySqlCommand(sql, con); //(操作语句和链接工具)
num = cmd.ExecuteNonQuery(); //执行操作返回影响行数
con.Close();
return "success" + num;
}
}
catch (Exception ex)
{
return ex.Message.ToString();
}
}
/// <summary>
/// MySQL select
/// </summary>
/// <param name="sql">select statement</param>
/// <param name="link">link statement</param>
/// <param name="record">Success:success; Fail:reason</param>
/// <returns>select result</returns>
public DataSet MySQL_Select(string sql, string link, out string record)
{
try
{
//储存数据的工具初始化
DataSet ds = new DataSet();
//相当于链接数据库的一个工具类（连接字符串）
using (MySqlConnection con = new MySqlConnection(link))
{
con.Open(); //打开
//用SqlConnection工具链接数据库，在通过sql查询语句查询结果现存入sql适配器
MySqlDataAdapter sda = new MySqlDataAdapter(sql, con); //(查询语句和连接工具)
sda.Fill(ds, "sample"); //将适配器数据存入DataSet工具中
con.Close(); //用完关闭SqlConnection工具
sda.Dispose(); //手动释放SqlDataAdapter
record = "success";
return ds;
}
}
catch (Exception ex)
{
DataSet dataSet = new DataSet();
record = ex.Message.ToString();
return dataSet;
}
}
