How to create SharePoint User Group and Assign Permissions

There are some cases where you want to create a group pro grammatically and want to assign permission. e.g. on the Feature receiver (Feature Activated) code.

In this post i am going to explain you how to create group and to assign permissions to this group.
First get the collection of site groups.

SPGroupCollection groups = web.SiteGroups;

web.BreakRoleInheritance(false);
Add the group to this collection. I have created "Test Group" in this example.

groups.Add("Test Group", web.CurrentUser, null, "");
SPGroup grp= web.SiteGroups["Test Group"];          

AllowMembersViewMembership property of this group to false.

This  Gets or sets a Boolean value that specifies whether only group members are    allowed to view the list of members in the group.
grp .OnlyAllowMembersViewMembership = false;
        grp .Update();

Now create a Role Assignment object of this group.

SPRoleAssignment asgn = new SPRoleAssignment(web.SiteGroups[ "Test Group"]);

Create a Role Definition, Here i have used the "Administrator" role, other available roles are

1) None
2) Guest
3) Reader
4) Contributor
5) WebDesigner
6) Administrator  

            SPRoleDefinition role = web.RoleDefinitions.GetByType(SPRoleType.Administrator);

Now assign the Role to the Role Assignment and add the  Role Assignment to the web and update the web

            asgn.RoleDefinitionBindings.Add(role);
            web.RoleAssignments.Add(asgn);
            web.Update();

Now deploy the solution and check the group and its permissions.

I have used this code on the feature activated code that creates group and assign permissions to this.