See you there.
Alessandro
How would you implement this using a Access Database?
You only need a single field to store you OR'ed bitmask value. Does not matter what database you use.
Hi - Great post :)
Forgive me if I have missed something here - I see how you grant permissions by adding the values to the "bucket" but how do you revoke a permisson? Can you post an example of the code to remove the "post" permission from a user who has all 3 permissons? I have an application using bitmasks to control runtime options and there are quite a few. Assembling some static combinations just isn't possible.
Help!
hi Lee, to clear a flag you can use the bitwise &(AND) operator combined with the ~(NOT). I have covered both the bitwise (&) / (~) operators in a previous post.
You can read about them here : weblogs.asp.net/.../bitwise-operators-in-c-or-xor-and-amp-amp-not.aspx
protected void Page_Load(object sender, EventArgs e)
{
int View = 1;
int Post = 2;
int Reply = 4;
int ViewAndPostAndReply = View | Post | Reply;
Response.Write(string.Format("<br /> {0}: View and post and reply", ViewAndPostAndReply));
int removePost = ViewAndPostAndReply &~Post;
Response.Write(string.Format("<br />{0}: Removed post", removePost));
if ((removePost & Post) == Post)
Response.Write("<br />Permission has post privileges");
else
Response.Write("<br />Permission does not have post privileges");
}
have a good day
Great post :)
I have one quick question. Can we use this with Code Security attributes (PrincipalPermissionAttributes)? Can you please share your thoughts on this.
Thanks
You could replace the static ints with the following, correct?
[Flags]
public enum testing
View = 1,
Post = 2,
Reply = 4,
ViewAndReply = 5
Great post! Regarding Anon's question - assigning ViewAndReply = 5 - I think that won't work, since 5 is not a power of two. Am I correct?
Thanks for the clean and simple explanation.
Great post! Thank you. The comment about negating or revoking a permission was helpful as well, as my current project requires both.
I do have to disagree with one point though. Us programmers tend to like our data stored in a way which closely mirrors what we intend to do with it, but it's always better to keep your data normalized even if you want to consume it in a flattened state.
For instance:
Let's say I have a Roles table:
RoleId RoleName
------ --------
1 View
2 Edit
And I have a linker table to a Users table called UserRoles
UserId RoleId
------ ------
In my code I have an enum for Roles:
public enum Roles
View,
Edit
Using Linq it's pretty easy to flatten my data into the "buckets" I prefer to work with:
(assume userId was passed into this method)
var userRoles = context.UserRoles
.Where(ur => ur.UserId == userId)
.Select(ur => new
UserId = ur.UserId,
RoleName = ur.Role.RoleName
})
.ToList();
return userRoles
.GroupBy(ur => ur.UserId)
.Select(s => new
UserId = s.Key.UserId,
RolesBitMask = r
.Select(m => Enum.Parse(typeof(Roles), m.RoleName))
.Aggrigate((allRoles, role) => allRoles | role)
//this returns a list of objects which each include the userId and the role bitmask. And my data is properly nomalized!!