C#---数据库访问通用类、Access数据库操作类、mysql类 .

//C# 数据库访问通用类 (ADO.NET)
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace XXX
{
    /// <summary>
    /// 针对SQL Server数据库操作的通用类  
   
    /// </summary>
    public class SqlDbHelper
    {
        private string connectionString;
        /// <summary>
        /// 设置数据库连接字符串
        /// </summary>
        public string ConnectionString
        {
            set { connectionString = value; }
        }
        /// <summary>
        /// 构造函数
        /// </summary>
        public SqlDbHelper()
            : this(ConfigurationManager.ConnectionStrings["Conn"].ConnectionString)
        {

        }
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="connectionString">数据库连接字符串</param>
        public SqlDbHelper(string connectionString)
        {
            this.connectionString = connectionString;
        }
        /// <summary>
        /// 执行一个查询，并返回结果集
        /// </summary>
        /// <param name="sql">要执行的查询SQL文本命令</param>
        /// <returns>返回查询结果集</returns>
        public DataTable ExecuteDataTable(string sql)
        {
            return ExecuteDataTable(sql, CommandType.Text, null);
        }
        /// <summary>
        /// 执行一个查询,并返回查询结果
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <returns>返回查询结果集</returns>
        public DataTable ExecuteDataTable(string sql, CommandType commandType)
        {
            return ExecuteDataTable(sql, commandType, null);
        }
        /// <summary>
        /// 执行一个查询,并返回查询结果
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <param name="parameters">Transact-SQL 语句或存储过程的参数数组</param>
        /// <returns></returns>
        public DataTable ExecuteDataTable(string sql, CommandType commandType, SqlParameter[] parameters)
        {
            DataTable data = new DataTable();//实例化DataTable，用于装载查询结果集
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand command = new SqlCommand(sql, connection))
                {
                    command.CommandType = commandType;//设置command的CommandType为指定的CommandType
                    //如果同时传入了参数，则添加这些参数
                    if (parameters != null)
                    {
                        foreach (SqlParameter parameter in parameters)
                        {
                            command.Parameters.Add(parameter);
                        }
                    }
                    //通过包含查询SQL的SqlCommand实例来实例化SqlDataAdapter
                    SqlDataAdapter adapter = new SqlDataAdapter(command);

                    adapter.Fill(data);//填充DataTable
                }
            }
            return data;
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="sql">要执行的查询SQL文本命令</param>
        /// <returns></returns>
        public SqlDataReader ExecuteReader(string sql)
        {
            return ExecuteReader(sql, CommandType.Text, null);
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <returns></returns>
        public SqlDataReader ExecuteReader(string sql, CommandType commandType)
        {
            return ExecuteReader(sql, commandType, null);
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <param name="parameters">Transact-SQL 语句或存储过程的参数数组</param>
        /// <returns></returns>
        public SqlDataReader ExecuteReader(string sql, CommandType commandType, SqlParameter[] parameters)
        {
            SqlConnection connection = new SqlConnection(connectionString);
            SqlCommand command = new SqlCommand(sql, connection);
            //如果同时传入了参数，则添加这些参数
            if (parameters != null)
            {
                foreach (SqlParameter parameter in parameters)
                {
                    command.Parameters.Add(parameter);
                }
            }
            connection.Open();
            //CommandBehavior.CloseConnection参数指示关闭Reader对象时关闭与其关联的Connection对象
            return command.ExecuteReader(CommandBehavior.CloseConnection);
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="sql">要执行的查询SQL文本命令</param>
        /// <returns></returns>
        public Object ExecuteScalar(string sql)
        {
            return ExecuteScalar(sql, CommandType.Text, null);
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <returns></returns>
        public Object ExecuteScalar(string sql, CommandType commandType)
        {
            return ExecuteScalar(sql, commandType, null);
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <param name="parameters">Transact-SQL 语句或存储过程的参数数组</param>
        /// <returns></returns>
        public Object ExecuteScalar(string sql, CommandType commandType, SqlParameter[] parameters)
        {
            object result = null;
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand command = new SqlCommand(sql, connection))
                {
                    command.CommandType = commandType;//设置command的CommandType为指定的CommandType
                    //如果同时传入了参数，则添加这些参数
                    if (parameters != null)
                    {
                        foreach (SqlParameter parameter in parameters)
                        {
                            command.Parameters.Add(parameter);
                        }
                    }
                    connection.Open();//打开数据库连接
                    result = command.ExecuteScalar();
                }
            }
            return result;//返回查询结果的第一行第一列，忽略其它行和列
        }
        /// <summary>
        /// 对数据库执行增删改操作
        /// </summary>
        /// <param name="sql">要执行的查询SQL文本命令</param>
        /// <returns></returns>
        public int ExecuteNonQuery(string sql)
        {
            return ExecuteNonQuery(sql, CommandType.Text, null);
        }
        /// <summary>
        /// 对数据库执行增删改操作
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <returns></returns>
        public int ExecuteNonQuery(string sql, CommandType commandType)
        {
            return ExecuteNonQuery(sql, commandType, null);
        }
        /// <summary>
        /// 对数据库执行增删改操作
        /// </summary>
        /// <param name="sql">要执行的SQL语句</param>
        /// <param name="commandType">要执行的查询语句的类型，如存储过程或者SQL文本命令</param>
        /// <param name="parameters">Transact-SQL 语句或存储过程的参数数组</param>
        /// <returns></returns>
        public int ExecuteNonQuery(string sql, CommandType commandType, SqlParameter[] parameters)
        {
            int count = 0;
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand command = new SqlCommand(sql, connection))
                {
                    command.CommandType = commandType;//设置command的CommandType为指定的CommandType
                    //如果同时传入了参数，则添加这些参数
                    if (parameters != null)
                    {
                        foreach (SqlParameter parameter in parameters)
                        {
                            command.Parameters.Add(parameter);
                        }
                    }
                    connection.Open();//打开数据库连接
                    count = command.ExecuteNonQuery();
                }
            }
            return count;//返回执行增删改操作之后，数据库中受影响的行数
        }
        /// <summary>
        /// 返回当前连接的数据库中所有由用户创建的数据库
        /// </summary>
        /// <returns></returns>
        public DataTable GetTables()
        {
            DataTable data = null;
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();//打开数据库连接
                data = connection.GetSchema("Tables");
            }
            return data;
        }

    }
}

//Access数据库-C# 操作类 代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;
using System.Data;

namespace XXX
{
    class AccessHelper
    {
        private string conn_str = null;
        private OleDbConnection ole_connection = null;
        private OleDbCommand ole_command = null;
        private OleDbDataReader ole_reader = null;
        private DataTable dt = null;

        /// <summary>
        /// 构造函数
        /// </summary>
        public AccessHelper()
        {
            conn_str =@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=‘D:\我的文档\Visual Studio 2008\Projects\AccessOperator\AccessOperator\bin\Debug\myDb.mdb‘";
            InitDB();
        }

        private void InitDB()
        {
            ole_connection =new OleDbConnection(conn_str);//创建实例
            ole_command =new OleDbCommand();
        }

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="db_path">数据库路径</param>
        public AccessHelper(string db_path)
        {
            conn_str ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=‘"+ db_path + "‘";
            InitDB();
        }

        /// <summary>
        /// 转换数据格式
        /// </summary>
        /// <param name="reader">数据源</param>
        /// <returns>数据列表</returns>
        privateDataTable ConvertOleDbReaderToDataTable(refOleDbDataReader reader)
        {
            DataTable dt_tmp =null;
            DataRow dr =null;
            int data_column_count = 0;
            int i = 0;

            data_column_count = reader.FieldCount;
            dt_tmp = BuildAndInitDataTable(data_column_count);

            if(dt_tmp == null)
            {
                return null;
            }

            while(reader.Read())
            {
                dr = dt_tmp.NewRow();

                for(i = 0; i < data_column_count; ++i)
                {
                    dr[i] = reader[i];
                }

                dt_tmp.Rows.Add(dr);
            }

            return dt_tmp;
        }

        /// <summary>
        /// 创建并初始化数据列表
        /// </summary>
        /// <param name="Field_Count">列的个数</param>
        /// <returns>数据列表</returns>
        private DataTable BuildAndInitDataTable(int Field_Count)
        {
            DataTable dt_tmp =null;
            DataColumn dc =null;
            int i = 0;

            if(Field_Count <= 0)
            {
                return null;
            }

            dt_tmp =new DataTable();

            for(i = 0; i < Field_Count; ++i)
            {
                dc =new DataColumn(i.ToString());
                dt_tmp.Columns.Add(dc);
            }

            return dt_tmp;
        }

        /// <summary>
        /// 从数据库里面获取数据
        /// </summary>
        /// <param name="strSql">查询语句</param>
        /// <returns>数据列表</returns>
        publicDataTable GetDataTableFromDB(string strSql)
        {
            if(conn_str == null)
            {
                return null;
            }
            
            try
            {
                ole_connection.Open();//打开连接

                if(ole_connection.State == ConnectionState.Closed)
                {
                    return null;
                }

                ole_command.CommandText = strSql;
                ole_command.Connection = ole_connection;

                ole_reader = ole_command.ExecuteReader(CommandBehavior.Default);

                dt = ConvertOleDbReaderToDataTable(ref ole_reader);

                ole_reader.Close();
                ole_reader.Dispose();
            }
            catch(System.Exception e)
            {
                Console.WriteLine(e.ToString());
            }
            finally
            {
                if(ole_connection.State != ConnectionState.Closed)
                {
                    ole_connection.Close();
                }
            }
            
            return dt;
        }

        /// <summary>
        /// 执行sql语句
        /// </summary>
        /// <param name="strSql">sql语句</param>
        /// <returns>返回结果</returns>
        public int ExcuteSql(stringstrSql)
        {
            int nResult = 0;

            try
            {
                ole_connection.Open();//打开数据库连接
                if(ole_connection.State == ConnectionState.Closed)
                {
                    return nResult;
                }

                ole_command.Connection = ole_connection;
                ole_command.CommandText = strSql;

                nResult = ole_command.ExecuteNonQuery();
            }
            catch(System.Exception e)
            {
                Console.WriteLine(e.ToString());
                return nResult;
            }
            finally
            {
                if(ole_connection.State != ConnectionState.Closed)
                {
                    ole_connection.Close();
                }
            }

            return nResult;
        }

        staticvoid Main(string[] args)
        {
            AccessHelper Helper =new AccessHelper();
            DataTable dt = Helper.GetDataTableFromDB("select * from test");

            foreach(DataRow dr in dt.Rows)
            {
                Console.WriteLine(dr[0].ToString()+" "+dr[1].ToString());
            }

            Console.WriteLine(Helper.ExcuteSql("insert into test(test) values (‘hello‘)"));
        }
    }
}

//C# mysql 类

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Data;
using System.Text.RegularExpressions;///
using MySql.Data.MySqlClient;

namespace XXX
{
    class MysqlConnection
    {
        MySqlConnection mysqlConnection;
        DataSet dataSet;
        string IP = null;
        string UserName = "root";
        string Password = "root";
        string Database = null;

        public MysqlConnection()
        {
            try
            {
                mysqlConnection = new MySqlConnection("datasource=20.0.0.20;username=root;password=root;database=sysinfo;charset=gb2312");
            }
            catch (MySqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        public MysqlConnection(string IP,string UserName,string Password,string Database)
        {
            try
            {
                string connectionString = "datasource=" + IP + ";username="+UserName+";password="+Password+";database=" + Database+ ";charset=gb2312" ;
                mysqlConnection = new MySqlConnection(connectionString);
            }
            catch (MySqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        public string MysqlInfo()
        {
            string mysqlInfo = null;
            try
            {
                mysqlConnection.Open();
                mysqlInfo += "Connection Opened." + Environment.NewLine;
                mysqlInfo += "Connection String:" + mysqlConnection.ConnectionString.ToString() + Environment.NewLine;
                mysqlInfo += "Database:" + mysqlConnection.Database.ToString() + Environment.NewLine;
                mysqlInfo += "Connection ServerVersion:" + mysqlConnection.ServerVersion.ToString() + Environment.NewLine;
                mysqlInfo += "Connection State:" + mysqlConnection.State.ToString() + Environment.NewLine;
            }
            catch (MySqlException ex)
            {
                Console.WriteLine("MySqlException Error:" + ex.ToString());
            }
            finally
            {
                mysqlConnection.Close();
            }
            return mysqlInfo;
        }
        public int MysqlCommand(string MysqlCommand)
        {
            try
            {
                mysqlConnection.Open();
                Console.WriteLine("MysqlConnection Opened.");
                MySqlCommand mysqlCommand = new MySqlCommand(MysqlCommand, mysqlConnection);
                return mysqlCommand.ExecuteNonQuery();
            }
            catch (MySqlException ex)
            {
                Console.WriteLine("MySqlException Error:" + ex.ToString());
                if (Regex.IsMatch(ex.ToString(), ""))
                {
                    MessageBox.Show("数据库已经存在唯一键值");
                }
            }
            finally
            {
                mysqlConnection.Close();
            }
            return -1;
        }     
        public DataView MysqlDataAdapter(string table)
        {
            DataView dataView = new DataView();
            try
            {
                mysqlConnection.Open();
                MySqlDataAdapter mysqlDataAdapter = new MySqlDataAdapter("Select * from " + table, mysqlConnection);
                dataSet = new DataSet();
                mysqlDataAdapter.Fill(dataSet, table);
                dataView = dataSet.Tables[table].DefaultView;
            }
            catch (MySqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                mysqlConnection.Close();
            }
            return dataView;
        }
    }//end class
}
//mysql 类2
class MySqlConnect
{
    static void Main()
    {
        string connString = @"Data Source=server;Database=mydb;User ID=username;Password=pwd;Command Logging=false";
        MySqlConnection conn = new MySqlConnection(connString);

        try
        {
            conn.Open();
            Console.WriteLine("Connection opened.");

            Console.WriteLine("Connection Properties:");
            Console.WriteLine("\tConnection String: {0}", conn.ConnectionString);
            Console.WriteLine("\tDatabase: {0}", conn.Database);
            Console.WriteLine("\tServerVersion: {0}",
               conn.ServerVersion);
            Console.WriteLine(
               "\tState: {0}",
               conn.State);
        }
        catch (MySqlException e)
        {
            Console.WriteLine("Error: " + e);
        }
        finally
        {
            conn.Close();
            Console.WriteLine("Connection closed.");
        }
    }
}

原文：http://www.cnblogs.com/waliy/p/4317778.html