Apply READ Permissions to SPGroup on all the folders within a document library

Question

I am doing a loop through for all the folders within a document library and wanna apply the Read permissions to a custom SPGroup.

How can i achieve the same?

Though i have written the code, by storing all the folder names from the doc lib into a generics ILIST object and then iterating thru these ILIST applying the permissions.

But it doesn't work. How to achieve the same? shouldn't i store the SPLISTITEM onto a ILIST OBJECT ?

IList<SPListItem> allFolderItems_BI = new List<SPListItem>();

            SPDocumentLibrary objBENCHMARKINDEXDocLibrary = 
         paramCurrentWeb.Lists.TryGetList("BenchmarkIndex") as 
       SPDocumentLibrary;
            if (objBENCHMARKINDEXDocLibrary != null && 
       objBENCHMARKINDEXDocLibrary.Folders.Count > 0)
            {
                SPQuery query = new SPQuery();
                //Condition to check the item type is folder or not
                query.Query = "<Where><Eq><FieldRef Name='FSObjType'/><Value 
              Type='Lookup'>1</Value></Eq></Where>";
                //Retrieve the items based on Query 
                SPListItemCollection folderItems = 
             objBENCHMARKINDEXDocLibrary.GetItems(query);
                string folderDetails = "";
                //Get the name and Url for the folder 
                foreach (SPListItem singleFolderitem in folderItems)
                {
                    folderDetails = singleFolderitem.Name;
                    allFolderItems_BI.Add(singleFolderitem);
                }
                if (allFolderItems_BI != null && allFolderItems_BI.Count > 
                   0)
                {
                    foreach (var singleFolderNamein_BI in allFolderItems_BI)
                    {
                        //if(singleFolderNamein_BI.HasUniqueRoleAssignments)
                        {
                            SPRoleAssignment 
           roleAssignmentFolderGroup_NPH_BI = new SPRoleAssignment(paramobjNPHDivGroup);
                            SPRoleDefinition 
              roleDefinitionFolderGroup_NPH_BI = 
        paramCurrentWeb.RoleDefinitions["NPD ReadILP"];
      roleAssignmentFolderGroup_NPH_BI.RoleDefinitionBindings.Add
         (roleDefinitionFolderGroup_NPH_BI);
     singleFolderNamein_BI.RoleAssignments.Add
       (roleAssignmentFolderGroup_NPH_BI);
                            //singleFolderNamein_BI.Update();
                          }
                      }
                   }
                //folderDetails += "Folder Name:" + item.Name + "<br/>Folder 
     URL:" + spWeb.Url + "/" + item.Url + "<br/>"; 
            }

Answer 1

Are you sure the permissions inheritance is stopped on the folders before calling RoleAssignments.Add?
You should try calling singleFolderNamein_BI.BreakRoleInheritance(true); first.

Something else: instead of retrieving all folders at once and then looping through them, you should definitely try a recursive approach: you get and process each folder at level 0, and for each of them you then get its child-folders to process them, etc.
Something like:

private void ProcessAllSubFolders(SPFolder folder)
{
    if (folder == null)
        return;

    foreach (SPFolder subFolder in folder.SubFolders)
    {
        SPRoleAssignment roleAssignmentFolderGroup_NPH_BI = new SPRoleAssignment(paramobjNPHDivGroup);
        SPRoleDefinition roleDefinitionFolderGroup_NPH_BI = paramCurrentWeb.RoleDefinitions["NPD ReadILP"];
        roleAssignmentFolderGroup_NPH_BI.RoleDefinitionBindings.Add(roleDefinitionFolderGroup_NPH_BI);
        singleFolderNamein_BI.RoleAssignments.Add (roleAssignmentFolderGroup_NPH_BI);

        ProcessAllSubFolders(subFolder);
    }
}

Usage:

 SPDocumentLibrary objBENCHMARKINDEXDocLibrary = paramCurrentWeb.Lists.TryGetList("BenchmarkIndex") as SPDocumentLibrary;
 ProcessAllSubFolders(objBENCHMARKINDEXDocLibrary.RootFolder);