Question

I need to organize some simple security in a class depends on value of the enum.
All that I can figure out is using attribute on a method and then run check then if it fails throw an exception.
Sample:

    [ModulePermission(PermissonFlags.Create)]
    public void CreateNew()
    {
        CheckPermission();
        System.Windows.Forms.MessageBox.Show("Created!");
    }
    protected void CheckPermission()
    {
        var method = new System.Diagnostics.StackTrace().GetFrame(1).GetMethod();
        if (!flags.HasFlag(method.GetCustomAttributes(true).Cast<ModulePermissionAttribute>().First().Flags))
        {
            throw new ApplicationException("Access denied");
        }
    }

is there more elegant or simple way to do this, like just to trigger an event when method run?

Answer 1

Not with an enum, but with strings – voila (enforced by the runtime, even in full-trust):

public static class PermissionFlags {
    public const string Create = "Create";
}

[PrincipalPermission(SecurityAction.Demand, Role = PermissionFlags.Create)]
public void CreateNew() {
    System.Windows.Forms.MessageBox.Show("Created!");
}

All you need to do now is to represent the user as a principal. This is done for you in ASP.NET, and there is a winform plugin (in VS2008 etc) to use ASP.NET for membership. It can be configured for vanilla winforms and WCF, too; at the most basic level, GenericPrincipal / GenericIdentity:

// during login...
string[] roles = { PermissionFlags.Create /* etc */ };
Thread.CurrentPrincipal = new GenericPrincipal(
    new GenericIdentity("Fred"), // user
        roles);

But you can write your own principal / identity models easily enough (deferred / cached access checks, for example).