有时候做数据的中转，SQLServer和Oracle这些大型数据库有点“杀鸡用牛刀”，而且会增加维护成本，这时可以使用“Access”数据库，尤其是处理“Winform”的时候。下面简单说一下
Access的数据访问类的使用方法，该类为静态方法，如果是多线程程序，可能会造成“数据库”连接之间的竞争。比如一个线程打开了数据库连接，还没有处理完，另一个线程就要关闭，这时就不能使用这个类了。
1、类如下。
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Data.OleDb;
namespace Model
{
/// <summary>
/// DataAccess 的摘要说明 C#操作Access实例解析
/// </summary>
public class DataAccess
{
protected static OleDbConnection conn = new OleDbConnection();
protected static OleDbCommand comm = new OleDbCommand();
public DataAccess()
{
//init C#操作Access实例解析
}
private static void openConnection()
{
if (conn.State == ConnectionState.Closed)
{
conn.ConnectionString = @"Provider=Microsoft.Jet.OleDb.4.0;Data Source=" + ConfigurationManager.AppSettings["myconn"];
//web.config文件里设定。
comm.Connection = conn;
try
{
conn.Open();
}
catch (Exception e)
{ throw new Exception(e.Message); }
}
}//打开数据库 C#操作Access实例解析
private static void closeConnection()
{
if (conn.State == ConnectionState.Open)
{
conn.Close();
conn.Dispose();
comm.Dispose();
}
}//关闭数据库 C#操作Access实例解析
public static void excuteSql(string sqlstr)
{
try
{
openConnection();
comm.CommandType = CommandType.Text;
comm.CommandText = sqlstr;
comm.ExecuteNonQuery();
}
catch (Exception e)
{
throw new Exception(e.Message);
}
finally
{ closeConnection(); }
}//执行sql语句 C#操作Access实例解析
public static OleDbDataReader dataReader(string sqlstr)
{
OleDbDataReader dr = null;
try
{
openConnection();
comm.CommandText = sqlstr;
comm.CommandType = CommandType.Text;
dr = comm.ExecuteReader(CommandBehavior.CloseConnection);
}
catch
{
try
{
dr.Close();
closeConnection();
}
catch { }
}
return dr;
}
//返回指定sql语句的OleDbDataReader对象，使用时请注意关闭这个对象。
public static void dataReader(string sqlstr, ref OleDbDataReader dr)
{
try
{
openConnection();
comm.CommandText = sqlstr;
comm.CommandType = CommandType.Text;
dr = comm.ExecuteReader(CommandBehavior.CloseConnection);
}
catch
{
try
{
if (dr != null && !dr.IsClosed)
dr.Close();
} //C#操作Access实例解析
catch
{
}
finally
{
closeConnection();
}
}
}
//返回指定sql语句的OleDbDataReader对象,使用时请注意关闭
public static DataSet dataSet(string sqlstr)
{
DataSet ds = new DataSet();
OleDbDataAdapter da = new OleDbDataAdapter();
try
{
openConnection();
comm.CommandType = CommandType.Text;
comm.CommandText = sqlstr;
da.SelectCommand = comm;
da.Fill(ds);
}
catch (Exception e)
{
throw new Exception(e.Message);
}
finally
{
closeConnection();
}
return ds;
}//返回指定sql语句的dataset C#操作Access实例解析
public static void dataSet(string sqlstr, ref DataSet ds)
{
OleDbDataAdapter da = new OleDbDataAdapter();
try
{
openConnection();
comm.CommandType = CommandType.Text;
comm.CommandText = sqlstr;
da.SelectCommand = comm;
da.Fill(ds);
}
catch (Exception e)
{
throw new Exception(e.Message);
}
finally
{
closeConnection();
}
}//返回指定sql语句的dataset C#操作Access实例解析
public static DataTable dataTable(string sqlstr)
{
DataTable dt = new DataTable();
OleDbDataAdapter da = new OleDbDataAdapter();
try
{
openConnection();
comm.CommandType = CommandType.Text;
comm.CommandText = sqlstr;
da.SelectCommand = comm;
da.Fill(dt);
}
catch (Exception e)
{
throw new Exception(e.Message);
}
finally
{
closeConnection();
}
return dt;
}//返回指定sql语句的datatable
public static void dataTable(string sqlstr, ref DataTable dt)
{
OleDbDataAdapter da = new OleDbDataAdapter();
try
{
openConnection();
comm.CommandType = CommandType.Text;
comm.CommandText = sqlstr;
da.SelectCommand = comm;
da.Fill(dt);
}
catch (Exception e)
{
throw new Exception(e.Message);
}
finally
{
closeConnection();
}
}//返回指定sql语句的datatable C#操作Access实例解析
public static DataView dataView(string sqlstr)
{
OleDbDataAdapter da = new OleDbDataAdapter();
DataView dv = new DataView();
DataSet ds = new DataSet();
try
{
openConnection();
comm.CommandType = CommandType.Text;
comm.CommandText = sqlstr;
da.SelectCommand = comm;
da.Fill(ds);
dv = ds.Tables[0].DefaultView;
}
catch (Exception e)
{
throw new Exception(e.Message);
}
finally
{
closeConnection();
}
return dv;
}
//返回指定sql语句的dataview C#操作Access实例解析
}
}
2、配置文件中连接字符串
<add key="myconn" value="ETLDatas.mdb;"/>
3、查询及判断数据存在
string IsExistSQL = " select * from ETLSettings where ETLName='" + name + "'";
if (DataAccess.dataTable(IsExistSQL).Rows.Count == 0)
{}
4、创建表
string ETLCreateSql = "Create TABLE " + name +
" ( DANo VARCHAR NOT NULL, DATime DATETIME NOT NULL, LogTime DATETIME NOT NULL, MeterType VARCHAR NOT NULL, MeterNo VARCHAR NOT NULL, Qty Decimal(18,6) NOT NULL )";
DataAccess.excuteSql(ETLCreateSql);
5、增加及删除记录
string ETLSql = " insert into ETLSettings values ('" + name + "','" + name + "'," + "1,0)";
ETLSql = " delete from ETLSettings where ETLName='" + name + "'";
6、删除表
drop table test
7、Access里插入时间需要“#XXXXXXXX#”这样。
DataAccess.excuteSql("insert into " + etlname + " (DANo,DATime,LogTime,MeterType,MeterNo,Qty,Status) values ('"+model.DANo+"',#"+model.DATime+"#,#"+model.LogTime+"#,'"+model.MeterType+"','"+model.MeterNo+"',"+model.Qty+",0)");
8、Access的连接数
Access是允许同时有255个打开的连接，注意是打开，打开并不表示就一定在执行查询。如果要执行查询，那是另外的事，和理论支持“255个并发连接”不冲突。
Access的连接是串行执行，没有并行执行模式。