stabes
string com = "select Count(*) from aspnet_Membership where IsApproved = 'IsApproved'";
Yes, that should be completely fine. This would only return the number of users with "Approved" accounts. Additionally, if your IsApproved field is actually a bit (which it should be based on the name), then you would want to use '1' to indicate it was true :
SELECT COUNT(*) FROM aspnet_Membership WHERE IsApproved = 1
Likewise, if you wanted to query and actually pull just those users, you might just use a SELECT * as opposed to the COUNT aggregate :
SELECT * FROM aspnet_Membership WHERE IsApproved = 1