Code thêm xóa sửa tìm kiếm trong c#

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

namespace BCTN.BLL
{
class KhoBaoChe
{

DAL.KetnoiCSDL da = new DAL.KetnoiCSDL();
public void ThemKBC(string _MaKho, string _TenKho)
{
string sql = "insert into KHOBAOCHE values(N'" + _MaKho + "',N'" + _TenKho + "')";
da.ExcuteNonQuery(sql);
}

public void XoaKBC(string _MaKho)
{
string sql = "Delete From KHOBAOCHE where MAKBC= '" + _MaKho + "'";
da.ExcuteNonQuery(sql);
}

public void SuaKBC(string _MaKho, string _TenKho)
{
string sql = "Update KHOBAOCHE set TENKBC= '" + _TenKho + "' where MAKBC= '" +_MaKho +"'";
http://MessageBox.Show(sql);
da.ExcuteNonQuery(sql);
}

//public DataTable SearchMAVT(string _MaVT)
//{
// string sql = "Select * from VITHUOC where MAVT like '%" + _MaVT + "%'";
// return da.GetTable(sql);
//}

//public DataTable SearchTENVT(string _TenVT)
//{
// string sql = "Select * from VITHUOC where TENVT like '%" + _TenVT + "%'";
// return da.GetTable(sql);
//}

public DataTable HienThiKBC()
{
string sql = "select * from KHOBAOCHE";
return da.GetTable(sql);
}
}
}

thực chất của câu lệnh tìm kiếm là câu lệnh select có where thui

Code:

"Select * from VITHUOC where TENVT like '%" + _TenVT + "%'"