This is the continuation of original question in this link.
Through the below code, I can able to fetch 1000 records but I have in total 6500++ records in my drive.
Here is an improved (IMO) version of EDR's great answer that does not repeat the listRequest code:
List allFiles = new List();
Google.Apis.Drive.v3.Data.FileList result = null;
while (true)
{
if (result != null && string.IsNullOrWhiteSpace(result.NextPageToken))
break;
FilesResource.ListRequest listRequest = service.Files.List();
listRequest.PageSize = 1000;
listRequest.Fields = "nextPageToken, files(id, name)";
if (result != null)
listRequest.PageToken = result.NextPageToken;
result = listRequest.Execute();
allFiles.AddRange(result.Files);
}