数据库访问通用类（Access）

连接字符串
<connectionStrings>
        <add name="DBaccess" providerName="System.Data.OleDb" connectionString="Provider=Microsoft.ACE.OLEDB.12.0; Data Source=E:\\DBaccess.accdb" />
    </connectionStrings>

代码如下：

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.OleDb;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DBAccessDemo
{
    internal class DBHelper
    {
        //<connectionStrings>
        //<add name = "connStr" connectionString="server=.;database=TestBase;uid=lyc;pwd=123456" providerName="System.Data.SqlClient"/>
        //</connectionStrings>
        private static readonly string connStr = ConfigurationManager.ConnectionStrings["DBaccess"].ConnectionString;


        //1、执行增删改查任务，Insert、Delete、Update
        //2、执行返回一个结果的查询
        //3、执行查询，返回sqldatareader
        //4、执行查询，返回dataset
        //5、执行查询，返回datatable

        /// <summary>
        /// 执行T-SQL ，返回受影响的行数  Insert Update Delete
        /// </summary>
        /// <param name="sql">slq语句</param>
        /// <param name="cmdType">sql命令类型，1=sql语句，2=存储过程</param>
        /// <param name="paras">sql参数</param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string sql, int cmdType, params OleDbParameter[] paras)
        {
            int count = 0;
            using (OleDbConnection conn = new OleDbConnection(connStr))
            {
                OleDbCommand cmd = new OleDbCommand(sql, conn);
                if (cmdType == 2) cmd.CommandType = CommandType.StoredProcedure;
                if (paras != null && paras.Length > 0) cmd.Parameters.AddRange(paras);
                conn.Open();
                count = cmd.ExecuteNonQuery();
                cmd.Parameters.Clear();
                conn.Close();
            }
            return count;
        }

        /// <summary>
        /// 执行查询，返回结果集第一行第一列的值，忽略其他行或列 object
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="cmdType"></param>
        /// <param name="paras"></param>
        /// <returns></returns>
        public static object ExecuteScalar(string sql, int cmdType, params OleDbParameter[] paras)
        {
            object result = null;
            using (OleDbConnection conn = new OleDbConnection(connStr))
            {
                OleDbCommand cmd = new OleDbCommand(sql, conn);
                if (cmdType == 2) cmd.CommandType = CommandType.StoredProcedure;
                if (paras != null && paras.Length > 0) cmd.Parameters.AddRange(paras);
                conn.Open();
                result = cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                conn.Close();
            }
            return result;
        }

        /// <summary>
        /// 执行查询，生成SqlDataReader
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="cmdType"></param>
        /// <param name="paras"></param>
        /// <returns></returns>
        /// <exception cref="Exception"></exception>
        public static OleDbDataReader ExecuteReader(string sql, int cmdType, params OleDbParameter[] paras)
        {
            OleDbDataReader result = null;
            OleDbConnection conn = new OleDbConnection(connStr);
            OleDbCommand cmd = new OleDbCommand(sql, conn);
            if (cmdType == 2) cmd.CommandType = CommandType.StoredProcedure;
            if (paras != null && paras.Length > 0) cmd.Parameters.AddRange(paras);
            try
            {
                conn.Open();
                result = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
            }
            catch (OleDbException ex)
            {
                conn.Close();
                throw new Exception("查询异常", ex);
            }

            return result;
        }

        /// <summary>
        /// 填充DataSet  一个或多个结果集 
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="cmdType"></param>
        /// <param name="paras"></param>
        /// <returns></returns>
        public static DataSet GetDataSet(string sql, int cmdType, params OleDbParameter[] paras)
        {
            DataSet dt = null;
            using (OleDbConnection conn = new OleDbConnection(connStr))
            {
                OleDbCommand cmd = new OleDbCommand(sql, conn);
                if (cmdType == 2) cmd.CommandType = CommandType.StoredProcedure;
                if (paras != null && paras.Length > 0) cmd.Parameters.AddRange(paras);
                OleDbDataAdapter adapter = new OleDbDataAdapter(cmd);
                conn.Open();
                adapter.Fill(dt);
                cmd.Parameters.Clear();
                conn.Close();
            }
            return dt;
        }

        public static DataTable GetDataTable(string sql, int cmdType, params OleDbParameter[] paras)
        {
            DataTable dt = new DataTable();
            using (OleDbConnection conn = new OleDbConnection(connStr))
            {
                OleDbCommand cmd = new OleDbCommand(sql, conn);
                if (cmdType == 2) cmd.CommandType = CommandType.StoredProcedure;
                if (paras != null && paras.Length > 0) cmd.Parameters.AddRange(paras);
                conn.Open();
                OleDbDataAdapter da = new OleDbDataAdapter(cmd);
                da.Fill(dt);
                cmd.Parameters.Clear();
                conn.Close();
            }
            return dt;
        }
    }
}

使用方法：

   //查询
     private void button1_Click(object sender, EventArgs e)
        {
            
            string sql = "select * from students";
            DataTable dt = DBHelper.GetDataTable(sql, 1);
            this.dataGridView1.DataSource = dt;

        }
//插入数据
        private void btnAdd_Click(object sender, EventArgs e)
        {
            string sql = "Insert into students (StuName,StuAge,StuId) values (@StuName,@StuAge,@StuId)";
            OleDbParameter[] paras = {
                new OleDbParameter ("@StuName","hanzq"),
                new OleDbParameter ("@StuAge",36),
                new OleDbParameter ("@StuId","1003" )
            };
            DBHelper.ExecuteNonQuery(sql, 1, paras);
        }
//删除数据
        private void btnDelete_Click(object sender, EventArgs e)
        {
            string sql = "Delete from students where StuId=@StuId";
            OleDbParameter[] paras = {
                
                new OleDbParameter ("@StuId","1003" )
            };
            DBHelper.ExecuteNonQuery (sql, 1, paras);
        }
    }