ADO连接问题

Question

用下面的方法初始化ADO连接时 
s:='Provider=SQLOLEDB.1;Password="'+c+'";Persist Security Info=True;UserID='+b+';Initial Catalog='+d+';Data Source='+a+'';
  ADOConnection1.connected:=False;
  ADOConnection1.Connectionstring:=''+s+'';
  ADOConnection1.connected:=True;
如果连接时出错,用什么信号可以来判断有错误出现?我想用它来弹出提示框

Answer 1

begin
s:='Provider=SQLOLEDB.1;Password="'+c+'";Persist Security Info=True;UserID='+b+';Initial Catalog='+d+';Data Source='+a+'';
  ADOConnection1.connected:=False;
  ADOConnection1.Connectionstring:= s;
  try
    ADOConnection1.connected:=True;
  except
    on E: Exception do ShowMessage(E.Message);
  end;
end;

Answer 2

on E: Exception do ShowMessage(E.Message);
是什么意思啊?

Answer 3

begin
s:='Provider=SQLOLEDB.1;Password="'+c+'";Persist Security Info=True;UserID='+b+';Initial Catalog='+d+';Data Source='+a+'';
  ADOConnection1.connected:=False;
  ADOConnection1.Connectionstring:= s;
  try
    ADOConnection1.connected:=True;
  except
    on E: Exception do 
     E.Create('数据库连接错误');   
  end;
end;
  

Answer 4

ADOConnection1.ConnectionString :=DBConnectionString ;
    try      
       ADOConnection1.Connected :=true;
    except
      showmessage('数据库连接错误');
    end;