how to check if a database exist?

how to check if a database exist?

I'm trying to connect to databases in sql server 2008 using delphi 7. I
have an array arr_foo that contains the names of databases. this is what
my script looks like:
for i:=3 to 5 do begin
sql := 'SELECT * FROM sys.databases WHERE name = '+quotedstr(arr_foo[i]);
adoquery1.close;
adoquery1.sql.text := sql;
adoquery1.open;
if not adoquery1.isempty then begin
adoconnection1.close;
adoconnection1.defaultdatabase := arr_foo[i];
adoconnection1.open;
end;
end;
at first, adoquery1 is already connected to adoconnection1. adoconnection1
is connected to //192.168.5.211 (which is my server).
the problem is that when I run the above script on delphi 7, it returns an
error 'Property value is invalid. Please make sure the value is typed
correctly' and stops at 'adoquery1.open' but when I run the query SELECT *
FROM sys.databases WHERE name = 'mydb3' in SQL SERVER Management Studio
2008 it returns 1 record normally. what is wrong with my script?