C#编写一个数据库查询的公共函数？如何调用

C#编写一个数据库查询的公共函数？怎么调用？
请问，怎么用C#编写一个数据库查询的公共函数？怎么调用？

[解决办法]
public static void Show()
{
SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=ST_StuManager;Integrated Security=True");

SqlDataAdapter sda = new SqlDataAdapter("select * from ST_student", con);
DataSet ds=new DataSet();

sda.Fill(ds,"stuTable");

foreach (DataRow item in ds.Tables["stuTable"].Rows)
{
Console.WriteLine(item[0]+"\t"+item[1]);
}


}
static void Main()
{
Show();
}

是不是这样啊
[解决办法]

C# code

/// <summary>        /// 返回一个可供操作DataTable，支持Sql和OleDB        /// </summary>        /// <param name="strSQL">SQL语句</param>        /// <param name="Connection">一个连接对象(OleDb或Sql类型)</param>        /// <returns></returns>        public static DataTable GetDataTable(string strSQL,IDbConnection Connection)        {                        DataTable dt     = new DataTable("BT");            DbDataAdapter da = null;                                        if(Connection is SqlConnection)            {                da = new SqlDataAdapter(strSQL, Connection as SqlConnection);            }            else            if(Connection is OleDbConnection)            {                da = new OleDbDataAdapter(strSQL, Connection as OleDbConnection);            }            else            {                throw new Exception("请传递一个OleDb或Sql类型的连接对象!");            }            da.Fill(dt);            return dt;        }
[解决办法]
 /// <summary>
       /// 执行SQL语句，返回影响的记录数
       /// </summary>
       /// <param name="SQLString">SQL语句</param>
       /// <returns>影响的记录数</returns>
       public static int ExecuteSql(string SQLString)
       {
           using (SqlConnection connection = new SqlConnection(connectionString))
           {
               using (SqlCommand cmd = new SqlCommand(SQLString, connection))
               {
                   try
                   {
                       connection.Open();
                       int rows = cmd.ExecuteNonQuery();
                       return rows;
                   }
                   catch (System.Data.SqlClient.SqlException e)
                   {
                       connection.Close();
                       throw e;
                   }
               }
           }
       }
C# code
/// <summary>        /// 执行查询语句，返回DataSet        /// </summary>        /// <param name="SQLString">查询语句</param>        /// <returns>DataSet</returns>        public static DataSet Query(string SQLString)        {            using (SqlConnection connection = new SqlConnection(connectionString))            {                DataSet ds = new DataSet();                try                {                    connection.Open();                    SqlDataAdapter command = new SqlDataAdapter(SQLString, connection);                    command.Fill(ds, "ds");                }                catch (System.Data.SqlClient.SqlException ex)                {                    throw new Exception(ex.Message);                }                return ds;            }        }