Unable to set permission on list for multiple spgroup

Question

I have a list to which I want to set permission to 2 site groups. Among them, one is contribute level and second is read.

My code for assigning the permission to list is:

private void SetCalendarListPermission(SPWeb web)
{
    SPList calendar = ListHelper.GetListByUrl(web.Lists, ListNames.CalendarUrl);
    if (calendar != null)
    {
        calendar.BreakRoleInheritance(true);
        SPGroup groupEventMangers = web.SiteGroups.GetByName(GroupsAndPermissions.GroupNames.EventManagers);
        SPRoleAssignment rAssignment = new SPRoleAssignment((SPPrincipal)groupEventMangers);
        SPRoleDefinition rDefinition = web.RoleDefinitions.GetByType(SPRoleType.Contributor);
        rAssignment.RoleDefinitionBindings.Add(rDefinition);
        calendar.RoleAssignments.Add(rAssignment);
        calendar.Update();
        SPGroup groupSiteVisitors = web.SiteGroups.GetByName(calendar.ParentWeb.Title + GroupsAndPermissions.GroupNames.Visitors);
        SPRoleAssignment rAssignmentVistor = new SPRoleAssignment((SPPrincipal)groupSiteVisitors);
        SPRoleDefinition rDefinitionVisitor = web.RoleDefinitions.GetByType(SPRoleType.Reader);
        rAssignment.RoleDefinitionBindings.Add(rDefinitionVisitor);
        calendar.RoleAssignments.Add(rAssignmentVistor);                
        calendar.Update();
    }
}

The first permission is set successfully but I am getting the error at line SPRoleDefinition rDefinitionVisitor = web.RoleDefinitions.GetByType(SPRoleType.Reader); which specifies that "Cannot add a role assignment with empty role definition binding collection.".

What am I missing?

Answer 1

When I add new role definition to role assignments collection I always create new instance of SPRoleDefinitionBindingsCollection and import it with SPRoleAssingment.ImportRoleDefinitionBindings method. It's not the only way I think, it's just my habit.

This code has always worked for me:

SPRoleAssignment roleAssignment = new SPRoleAssignment(principal);
SPRoleDefinition roleDefinition = new SPRoleDefinition();
roleDefinition = web.RoleDefinitions.GetByType(SPRoleType.Reader);
SPRoleDefinitionBindingCollection roleDefinitionBindingCollection = new SPRoleDefinitionBindingCollection();
roleDefinitionBindingCollection.Add(roleDefinition);
roleAssignment.ImportRoleDefinitionBindings(roleDefinitionBindingCollection);
web.AllowUnsafeUpdates = true;
list.RoleAssignments.Add(roleAssignment);
web.AllowUnsafeUpdates = false;

Also try setting SPWeb.AllowUnsafeUpdates = true; because some operations may reset it automatically.

Answer 2

By trying some code samples I found the solution:

I just needed to change a single line of code. The line is: calendar.BreakRoleInheritance(true); The reason was if I place true then the roles were copied after the inheritance was break, I corrected using calendar.BreakRoleInheritance(false); that now no groups will be there and new groups will be applied to the list.

Hope this helps others too!!