Retrieve All Documents from all Subfolders in a Document Library - CSOM

Question

I am using the client side object model approach C# in order to retrieve all list items from a document library containing sub folders. I checked out the MSDN documentation and I am stuck as to why I cannot get the field property, or if I am even doing this right.

    NetworkCredential credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
            ClientContext clientcontext = new ClientContext(Resources.defaultSPSite);
            clientcontext.Credentials = credentials;

            //Load Libraries from SharePoint
            //Web site = clientcontext.Web;
            clientcontext.Load(clientcontext.Web.Lists);
            clientcontext.ExecuteQuery();


            //List sharedDocumentsList = clientcontext.Web.Lists.GetByTitle("TestLDOCS");
            //CamlQuery camlQuery = new CamlQuery();
            //camlQuery.ViewXml = @"<View Scope='Recursive'><Query></Query></View>";

            foreach (List list in clientcontext.Web.Lists)
            {
                clientcontext.Load(list);
                clientcontext.ExecuteQuery();
                //list.TemplateFeatureId.ToString().Equals("") &&
                    string baseType =  list.BaseType.ToString();
                    string listTitle = list.Title.ToString();
                    if (list.BaseType.ToString().Equals("DocumentLibrary", StringComparison.InvariantCultureIgnoreCase) && list.Title.ToString().Equals("TestLDOCS", StringComparison.InvariantCultureIgnoreCase))
                    {
                        foreach (Folder subFolder in list.RootFolder.Folders)
                        {
                            foreach (File f in subFolder.Files)
                            {
                                Console.WriteLine((string) f.Title);                     
                            }
                        }
                    }
             }
        }

The error that I am receiving is that the "foreach(File f in subFolder.Files)" collection may not be initialized error. Is there anyway to get the field values of all documents in every subfolder within a document library using CSOM?

I know you can strongly type the field values as well with a list item ie (listItem["fieldName"]). Should I go this route instead?

Answer 1

foreach (List list in clientcontext.Web.Lists)
        {
            clientcontext.Load(list);
            clientcontext.ExecuteQuery();
            //list.TemplateFeatureId.ToString().Equals("") &&
                string baseType =  list.BaseType.ToString();
                string listTitle = list.Title.ToString();
                if (list.BaseType.ToString().Equals("DocumentLibrary", StringComparison.InvariantCultureIgnoreCase) && list.Title.ToString().Equals("TestLDOCS", StringComparison.InvariantCultureIgnoreCase))
                {
                    foreach (Folder subFolder in list.RootFolder.Folders)
                    {
           clientcontext.Load(subFolder.Files);
                   clientcontext.ExecuteQuery();
                        foreach (File f in subFolder.Files)
                        {
                            Console.WriteLine((string) f.Title);                     
                        }
                    }
                }
         }
    }

Answer 2

Some recommendations:

1) Prefer ClientRuntimeContext.LoadQuery method to load a specific lists, for example:

var lists = ctx.LoadQuery(ctx.Web.Lists.Where(l => l.BaseType == BaseType.DocumentLibrary));
ctx.ExecuteQuery();

2) Since SharePoint SCOM supports Request Batching it is recommended to minimize the number of requests to the server. The following example demonstrates how to perform a single request to the server in order to load all files from document libraries:

foreach (var list in lists)
{
    var items = list.GetItems(CreateAllFilesQuery());
    ctx.Load(items, icol => icol.Include(i => i.File));
    results[list.Title] = items.Select( i=>i.File);
}
ctx.ExecuteQuery();

3) Prefer to load all files via CAML query as demonstrated below:

public static CamlQuery CreateAllFilesQuery()
{
   var qry = new CamlQuery();
   qry.ViewXml ="<View Scope=\"RecursiveAll\"><Query><Where><Eq><FieldRef Name=\"FSObjType\" /><Value Type=\"Integer\">0</Value></Eq></Where></Query></View>";
   return qry;
}

Then the following example will return all the files in library:

var items = list.GetItems(CreateAllFilesQuery());
ctx.Load(items, icol => icol.Include(i => i.File));
ctx.ExecuteQuery();
var files = items.Select( i=>i.File).ToList();

It is more optimized way of loading specific lists from performance perspective

Complete example

How to load all files from document libraries using SharePoint CSOM:

using (var ctx = new ClientContext(webUri))
{

     var results = new Dictionary<string, IEnumerable<File>>();
     var lists = ctx.LoadQuery(ctx.Web.Lists.Where(l => l.BaseType == BaseType.DocumentLibrary));
     ctx.ExecuteQuery();
     foreach (var list in lists)
     {
         var items = list.GetItems(CreateAllFilesQuery());
         ctx.Load(items, icol => icol.Include(i => i.File));
         results[list.Title] = items.Select( i=>i.File);
     }
     ctx.ExecuteQuery();

     //Print results
     foreach (var result in results)
     {
         Console.WriteLine("List: {0}",result.Key);
         foreach (var file in result.Value)
         {
             Console.WriteLine("File: {0}", file.Name);
         }
      }        
}