When do we use Demand and when do we use Assert?

Hi, I am a newbie in .net security so please bear with me. Normally when I access a resource let say a file, I instantiate a Permission e.g. FileIOPermission FIO = new FileIOPermission(FileIOPermissionAccess.Append | FileIOPermissionAccess.Read | FileIOPermissionAccess.Write, @"C:\TEMP\whatever.txt"); // I do this normally try{ FIO.Demand(); FIO.Assert() // ... write to the file etc. } catch(Exception e) { //... do some exception logging } finally { CodeAccessPermission.RevertAssert(); } My question is this: if I removed the Demand() statement will it affect the way I access the file? I've read that the Demand method walks thru the stack so it may affect my applications overall performance but I haven't noticed any differences when I commented it out. Maybe I am mixing up the two that's why I'm confused. Any help or clarification would be highly appreciated. Hanggang sa muli, Tikbalang.

The very first thing is that do not b in a confusion that removin demand statements will ever improve ur specified codes' performance. To make it more clear, .NET Runtime automatically performs appropriate actions of "Demand" method on execution of statements that require permissions. The same is the reason why it would not affect the way u access file coz Demand is always executed in any case by runtime automatically. Tikbalang, there is no use of demand statements untill ur function is being called by anyother function. if u want to increase performance by preventing stackwalk u will have to add appropriate attributes to ur methods or assembly which will effectively suppress the automatic stackwalk done by Runtime. can u see any use of ur demand statements if .NET Runtime does it automatically???:)