How to grant user permission to certain folders using Client Object Model?

Question

So far I am able to grant user certain permission with the following code:

    ClientContext context = new ClientContext("http://myRealURL");
    Principal user = context.Web.EnsureUser(@"myLoginAccout");

    RoleDefinition readDef = context.Web.RoleDefinitions.GetByName("Read");
    RoleDefinitionBindingCollection roleDefCollection = new RoleDefinitionBindingCollection(context);
    roleDefCollection.Add(readDef);
    RoleAssignment newRoleAssignment = context.Web.RoleAssignments.Add(user, roleDefCollection);

    context.ExecuteQuery(); 

The code above works fine, now my task is to add the user permission only to certain folders with C# code. For example, under Libraries, I have a library called JZhu, and inside JZhu, I have two folders folder1 and folder2. Is it possible to change the access permission on these two folders with Client Object Model?

Answer 1

The following example demonstrates how to customize access to folder via CSOM. There are two steps:

1. assign unique permissions for a Folder since by default folder inherits permissions from the parent object (List)
2. grant user permissions to a folder

Example:

Principal user = ctx.Web.EnsureUser(accountName);
var folder = ctx.Web.GetFolderByServerRelativeUrl(folderUrl);
var roleDefinition = ctx.Site.RootWeb.RoleDefinitions.GetByType(RoleType.Reader);  //get Reader role
var roleBindings = new RoleDefinitionBindingCollection(ctx) { roleDefinition };
folder.ListItemAllFields.BreakRoleInheritance(true, false);  //set folder unique permissions
folder.ListItemAllFields.RoleAssignments.Add(user, roleBindings);
ctx.ExecuteQuery();

, where folderUrl parameter corresponds to server relative url for a folder,

for example /news/documents/archive for the following structure:

News (site)
  |
  Documents (library)
     |
     Archive (folder)