C# OleDBHelper（数据库访问公共接口）

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

namespace OleDbHelper_TEST
{
public class OleDbHelper
{
public OleDbHelper() { }

private static OleDbConnection Conn;
private static OleDbCommand Cmd;
private static OleDbDataAdapter Da;
private static DataSet Ds;
private static DataTable Dt;
private static string strConn = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=c:\\a.mdb";

public static void setConn(string FileName)
{
strConn = "Provider=Microsoft.Jet.OleDb.4.0;Data Source="+FileName;
}

/// <summary>
/// 打开连接
/// </summary>
public static void Open()
{
Conn = new OleDbConnection();
Cmd = new OleDbCommand();
if (Conn.State.Equals(ConnectionState.Closed))
{
Conn.ConnectionString = strConn;
Conn.Open();
}
Cmd.Connection = Conn;
}

/// <summary>
/// 关闭连接
/// </summary>
public static void Close()
{
if (Conn.State.Equals(ConnectionState.Open))
{
Conn.Close();
Conn.Dispose();
}
}

/// <summary>
/// 执行ExecuteNonQuery()
/// </summary>
/// <param name="sql">SQL语句</param>
/// <returns></returns>
public static int ExecuteCmd(string sql)
{
try
{
Open();
Cmd.CommandText = sql;
return Cmd.ExecuteNonQuery();
}
catch (Exception e)
{
throw new Exception(e.Message, e);
}
finally
{
Close();
}
}

/// <summary>
/// DataSet类
/// </summary>
/// <param name="sql">SQL语句</param>
/// <returns></returns>
public static DataSet GetDataSet(string sql)
{
try
{
Open();
Cmd.CommandText = sql;
Da = new OleDbDataAdapter();
Da.SelectCommand = Cmd;
Ds = new DataSet();
Da.Fill(Ds);
return Ds;
}
catch (Exception e)
{
throw new Exception(e.Message, e);
}
finally
{
Close();
}
}

/// <summary>
/// DataTable 类
/// </summary>
/// <param name="sql">SQL语句</param>
/// <returns></returns>
public static DataTable GetDataTable(string sql)
{
try
{
Open();
Cmd.CommandText = sql;
Da = new OleDbDataAdapter();
Da.SelectCommand = Cmd;
Dt = new DataTable();
Da.Fill(Dt);
return Dt;
}
catch (Exception e)
{
throw new Exception(e.Message, e);
}
finally
{
Close();
}
}

/// <summary>
/// 执行 ExecuteScalar
/// </summary>
/// <param name="sql">SQL语句</param>
/// <returns></returns>
public static object ExecuteScalar(string sql)
{
try
{
Open();
Cmd.CommandText = sql;
return Cmd.ExecuteScalar();
}
catch (Exception e)
{
throw new Exception(e.Message, e);
}
finally
{
Close();
}
}
}
}