DBHelper

public static string ConnString = "server=.;database=flightDB;Integrated Security=true";
private static SqlConnection Conn = null;

//初始化数据库链接
private static void InitConnection()
{
if (Conn == null)
Conn = new SqlConnection(ConnString);
if (Conn.State == ConnectionState.Closed)
Conn.Open();
if (Conn.State == ConnectionState.Broken)
{
Conn.Close();
Conn.Open();
}
}

//查询，获取DataReader
public static SqlDataReader GetDataReader(string sqlStr)
{
InitConnection();
SqlCommand cmd = new SqlCommand(sqlStr, Conn);
return cmd.ExecuteReader(CommandBehavior.CloseConnection);
}

//查询，获取DataSet
public static DataSet GetDataSet(string sqlStr)
{
InitConnection();
DataSet ds = new DataSet();
SqlDataAdapter dap = new SqlDataAdapter(sqlStr, Conn);
dap.Fill(ds);
Conn.Close();
return ds;
}

//查询，获取DataTable
public static DataTable GetDataTable(string sqlStr)
{
return GetDataSet(sqlStr).Tables[0];
}

//增改删
public static bool ExecuteNonQuery(string sqlStr)
{
InitConnection();
SqlCommand cmd = new SqlCommand(sqlStr, Conn);
int result = cmd.ExecuteNonQuery();
Conn.Close();
return result > 0;
}

//执行集合函数
public static object ExecuteScalar(string sqlStr)
{
InitConnection();
SqlCommand cmd = new SqlCommand(sqlStr, Conn);
object result = cmd.ExecuteScalar();
Conn.Close();
return result;
}