寫在前面：
常用數據庫：
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，通常一個項目會大量用的數據庫的各種基本操作，因此小編幾個常見的數據庫的操作封裝成了一個dll方便后續的開發使用。本文則主要是記錄了C#對MySQL的連接、增、刪、改、查的基本操作，如有什么問題還請各位大佬指教。后續也將對其他幾個常用的數據庫進行相應的整理。話不多說，直接開始碼代碼。
引用：
MySQL的引用需要去手動下載
using MySql.Data.MySqlClient; //MySQL引用集
using System.Data; //DataSet引用集
先聲明一個MySqlConnection 便於后續使用。
private MySqlConnection mysql_con;
MySQL打開：
/// <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關閉：
/// <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的增刪改：
/// <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
{
//儲存數據的工具初始化
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;
}
}
小編發現以上這種封裝方式還是很麻煩，每次對MySQL進行增刪改查的時候還得先打開數據庫，最后還要關閉，實際運用起來比較麻煩。因此對上面兩個增刪改查的方法進行了重載，在每次進行操作時都先打開數據庫，然后關閉數據庫。
/// <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();
//操作數據庫的工具SqlCommand
MySqlCommand cmd = new MySqlCommand(sql, con); //(操作語句和鏈接工具)
num = cmd.ExecuteNonQuery(); //執行操作返回影響行數
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
{
//儲存數據的工具初始化
DataSet ds = new DataSet();
//相當於鏈接數據庫的一個工具類（連接字符串）
using (MySqlConnection con = new MySqlConnection(link))
{
con.Open(); //打開
//用SqlConnection工具鏈接數據庫，在通過sql查詢語句查詢結果現存入sql適配器
MySqlDataAdapter sda = new MySqlDataAdapter(sql, con); //(查詢語句和連接工具)
sda.Fill(ds, "sample"); //將適配器數據存入DataSet工具中
con.Close(); //用完關閉SqlConnection工具
sda.Dispose(); //手動釋放SqlDataAdapter
record = "success";
return ds;
}
}
catch (Exception ex)
{
DataSet dataSet = new DataSet();
record = ex.Message.ToString();
return dataSet;
}
}