removing then setting custom permissions for a list

Question

I have been looking around for few days, but couldn't really figure out, how I will be able to do this.

what I am doing is removing all permissions of a given list using following code,

  using (SPSite site = new SPSite("https://abc2020.development.com/portol/../default.aspx"))
            {
                using (SPWeb web = site.OpenWeb())
                {
                    SPList myList = web.Lists["listname"];
                    myList.BreakRoleInheritance(true);
                    while (myList.RoleAssignments.Count > 0)
                        myList.RoleAssignments.Remove(0);
                }
            }

Now I want to get all the Groups/Users who have permission to web(where this list is created) and give them all my custom level permission "ABC permission level" that I created on top level sitecollection.

Oh yes there will be a user "System Account" who I wanna give FULL Control.

I looked around on google and find this code Snippet but I got no clue how can I integrate it with my situation.

    SPRoleAssignment roleAssignment = new SPRoleAssignment("dom\\user", "user@dom", "user", "some notes");
SPRoleDefinition roleDefinition = web.RoleDefinitions.GetByType(SPRoleType.Contributor);
roleAssignment.RoleDefinitionBindings.Add(roleDefinition);
if (!myList.HasUniqueRoleAssignments)
{
    myList.BreakRoleInheritance(true); // Ensure we don't inherit permissions from parent
} 
myList.RoleAssignments.Add(roleAssignment);
myList.Update();

Cheers Ali

Answer 1

I don't know how you're going to select the users but one option could be to loop through the Users collection of one/all of the web.Groups

For each User (which can be an AD-group) create a SPRoleAssignment and add web.RoleDefinitions["ABC permission level"] as RoleDefintionBinding before adding the RoleAssignment to the list.

For the "System Account" use web.RoleDefinitions.GetByType("Administrator")