C#：数据库操作（待补充）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;
using System.Data;
using System.Windows.Forms;

namespace MyCommanHelper
{
    public class DataBaseHelper
    {

    #region 字段变量

        public static volatile string Connstring = "";
        private static volatile OleDbConnection connection = null;

    #endregion

    #region 方法

        #region Access

        // Methods
        /// <summary>
        /// 获取Access2003连接字符串
        /// </summary>
        /// <param name="sFilePath">Access文件路径</param>
        /// <returns></returns>
        public static string GetAccess2003ConnectionString(string sFilePath)
        {
            return ("Provider=Microsoft.JET.OLEDB.4.0;data source=" + sFilePath);
        }

        /// <summary>
        /// 获取Access2007连接字符串
        /// </summary>
        /// <param name="sFilePath">Access文件路径</param>
        /// <returns></returns>
        public static string GetAccess2007ConnectionString(string sFilePath)
        {
            return ("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + sFilePath);
        }

        #endregion

        #region SqlServer

        #endregion

        #region Oracle
        public static string GetOracleBlobConnectionString(string sUser, string sPassword, string sServiceName)
        {
            return ("server=oratest;Data Source=" + sServiceName + ";User ID=" + sUser + ";Password=" + sPassword);
        }

        public static string GetOracleConnectionString(string sUser, string sPassword, string sServiceName)
        {
            return ("Provider=OraOLEDB.Oracle.1;Data Source=" + sServiceName + ";User ID=" + sUser + ";Password=" + sPassword);
        }

        #endregion

        #region 公共

        /// <summary>
        /// 初始化新实例
        /// </summary>
        /// <returns></returns>
        public static bool Init()
        {
            try
            {
                connection = new OleDbConnection(Connstring);
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

        /// <summary>
        /// 执行非查询操作
        /// </summary>
        /// <param name="sqlStr">执行SQL语句</param>
        /// <returns>返回影响行数，值为-1 表示未创建连接实例或执行语句错误</returns>
        public static int ExecNonQuery(string sqlStr)
        {
            int rslt = -1;

            if (null == connection)
            {
                MessageBox.Show("无连接实例！");
                return rslt;
            }

            try
            {
                if (connection.State == ConnectionState.Closed)
                {
                    connection.Open();
                }
                OleDbCommand command = new OleDbCommand(sqlStr, connection);
                rslt = command.ExecuteNonQuery();
                command.Dispose();
                //connection.Close();
                //connection.Dispose();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                connection.Close();
            }
            return rslt;
        }

        /// <summary>
        /// 获取只包含指定的数据的数据集
        /// </summary>
        /// <param name="sqlStr">Sql指令</param>
        /// <param name="sTable">指定数据</param>
        /// <returns>数据集 值为null 表示未创建连接实例</returns>
        public static DataSet ExecQuery(string sqlStr, string sTable)
        {
            DataSet set2 = null;
            if (null == connection)
            {
                MessageBox.Show("无连接实例！");
                return set2;
            }

            try
            {
                if (connection.State == ConnectionState.Closed)
                {
                    connection.Open();
                }
                OleDbDataAdapter adapter = new OleDbDataAdapter(sqlStr, connection);
                DataSet dataSet = new DataSet();
                if (dataSet.Tables.Contains(sTable))
                {
                    dataSet.Tables[sTable].Clear();
                }
                adapter.Fill(dataSet, sTable);
                set2 = dataSet;
            }
            catch (Exception exception)
            {
                throw exception;
            }
            finally
            {
                connection.Close();
                //connection.Dispose();
                //connection = null;
            }
            return set2;
        }

        /// <summary>
        /// 获得第一行数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="sTable"></param>
        /// <returns></returns>
        public static DataRow GetFirstRow(string sql, string sTable)
        {
            DataRow row = null;
            DataSet set = ExecQuery(sql, sTable);
            if (set.Tables[sTable].Rows.Count > 0)
            {
                row = set.Tables[sTable].Rows[0];
            }
            return row;
        }

        /// <summary>
        /// 获得第一行第一个字段的值
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="sTable"></param>
        /// <returns></returns>
        public static string GetFirstFieldValue(string sql, string sTable)
        {
            string str = "";
            DataSet set = ExecQuery(sql, sTable);
            if (set.Tables[sTable].Rows.Count > 0)
            {
                DataRow row = set.Tables[sTable].Rows[0];
                str = row[0].ToString();
            }
            return str;
        }

        /// <summary>
        /// 释放连接资源
        /// </summary>
        public static void Dispose()
        {
            if (null != connection)
            {
                if (connection.State != ConnectionState.Closed)
                {
                    connection.Close();
                }
                connection.Dispose();
                connection = null;
            }
        }

        #endregion

    #endregion

    }
}