下面代码如何捕获并处理数据库连接错误?

Question

我想当数据库连接错误的时候，捕获并处理异常。处理是返回当前界面停止下面的所有操作，捕获异常后用messagebox提示出错原因.                    SqlConnection con = new SqlConnection(conn_str);
                    SqlCommand command1 = new SqlCommand(sql_str, con);
                    con.Open();
                    SqlDataReader rs1 = command1.ExecuteReader();
                    try
                    {
                        while (rs1.Read())
                        {
                            if(File.Exists(rs1[3].ToString()))
                            {
                            cj_names = rs1[1].ToString();
                            cj_pic_path = rs1[3].ToString();
                            cj_id = rs1[0].ToString();
                            names.Add(cj_names);
                            id.Add(cj_id);
                            lst.Add(Image.FromFile(cj_pic_path));
                            //重新从数据库装载LIST图片信息
                            }
                        }
                    }
                    catch(FileNotFoundException)
                    {
                        //忽略路径无效图片
                    }
                    finally
                    {
                        con.Close();
                        rs1.Close();
                    }

Answer 1

                    try
                    {
                    SqlConnection con = new SqlConnection(conn_str);
                    SqlCommand command1 = new SqlCommand(sql_str, con);
                    con.Open();
                    SqlDataReader rs1 = command1.ExecuteReader();
                        while (rs1.Read())
                        {
                            if(File.Exists(rs1[3].ToString()))
                            {
                            cj_names = rs1[1].ToString();
                            cj_pic_path = rs1[3].ToString();
                            cj_id = rs1[0].ToString();
                            names.Add(cj_names);
                            id.Add(cj_id);
                            lst.Add(Image.FromFile(cj_pic_path));
                            //重新从数据库装载LIST图片信息
                            }
                        }
                    }
                    catch(FileNotFoundException)
                    {
                        //忽略路径无效图片
                    }
                    finally
                    {
                        con.Close();
                        rs1.Close();
                    }

Answer 2

提示 ,错误.
finally                    
{
      con.Close();
      rs1.Close();                 
}
错误 1 当前上下文中不存在名称“con” C:\cj_sys\cj_sys\Form1.cs 90 25 cj_sys
错误 1 当前上下文中不存在名称“rs1” C:\cj_sys\cj_sys\Form1.cs 90 25 cj_sys而且这样只捕获了文件不存在的异常呀，数据库的异常怎么捕获？

Answer 3

 catch(Sysetem.Exception ex)
                    {
                        //忽略路径无效图片
                    MessageBox.Show("Error",ex.Message)
                    }

Answer 4

用catch(exception ex)这是捕获所有错误，如果只想捕获数据库的错误的话，可以看看都有哪些错误，另外，在你的finally那里，直接写
con.Close();
rs1.Close();
会有问题，一是顺序反了，先关闭rs1，然后再关闭数据库连接con，另外，如果con在open的时候就出错咯，那你close的话，同样也会报告错误，所以你在关闭con之前，要先判断下其状态