How do I get List from RootFolder in CSOM?

Question

I have a utility function to copy documents from one folder to another folder in SharePoint Online using C#/CSOM. It works well for subfolders, but I am having issues with RootFolders for libraries.

For example, this will get the root list for a subfolder. I use the return List for other tasks like copying content types, fields, and other configuration for the copied documents:

public static List Foo(Folder bar)
{
     return bar.ListItemAllFields.ParentList;
}

Problem is, when I pass a List.RootFolder object to this function (which uses the Folder class), there is an error because ListItemAllFields is null. The question is how do I get the parent list with just the Folder as a parameter if the folder's ListItemAllFields property is null? This does not work:

public static void FooBar(List list)
{
     List self = Foo(list.RootFolder); 
}
public static List Foo(Folder bar)
{
     return bar.ListItemAllFields.ParentList;
}

Thanks

Answer 1

I have written utility for SPO site to copy entire library folders and files. The syntax I am using as follows

List srcLst = srcCtx.Web.Lists.GetByTitle(SourceListTitle);
var srcLibRootFolder = srcLst.RootFolder;
srcCtx.Load(srcLibRootFolder);
srcCtx.ExecuteQuery();

After Load operation, I am getting root folder object.

Answer 2

If you have the URL of the folder, you can use Web.GetList(), and pass the url in:

var list = ctx.Web.GetList(folder.ServerRelativeUrl);

Not sure if this is viable in your scenario, but it's one option.

MSDN documentation for Web.GetList().