关于C#中语法conn.Close();的问题，麻烦帮忙看一下！

Question

/// <summary>
/// 输出
/// </summary>
/// <param name="SQL"></param>
public SqlDataReader Output(string SQL)
{
SqlConnection conn = ConnOpen();//数据库连接！
SqlDataReader ds;
try
{
conn.Open();
SqlCommand cmd = new SqlCommand(SQL, conn);
ds = cmd.ExecuteReader(CommandBehavior.CloseConnection);
}
catch (Exception e)
{
throw e;
}
return ds;
}

/********/
conn.Close();无法断开连接。

Answer 1

直接在try{............}catch{}finally{conn.Close();}关闭或者 用using自动打开，关闭连接using (SqlConnection conn = ConnOpen()){//要写的代码}

Answer 2

conn.Open();SqlCommand cmd = new SqlCommand(SQL, conn);ds = cmd.ExecuteReader(CommandBehavior.CloseConnection);放这个位置conn.Close（）;

Answer 3

/// <summary>/// 输出/// </summary>/// <param name="SQL"></param>public SqlDataReader Output(string SQL){SqlConnection conn = ConnOpen();//数据库连接！SqlDataReader ds;try{conn.Open();SqlCommand cmd = new SqlCommand(SQL, conn);ds = cmd.ExecuteReader(CommandBehavior.CloseConnection);}catch (Exception e){throw e;}return ds;conn.Close();//位置放错了}