using System;
using System.IO;
using System.Linq;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Wordprocessing;
using Microsoft.SharePoint.Client;
// The following using directive resolves the ambiguity
// between the System.IO.File class and Microsoft.SharePoint.Client.File
// class.
using ClientOM = Microsoft.SharePoint.Client;
using System.Net;
using System.Data;

class Program
{
    static private void CopyStream(Stream source, Stream destination)
{
    byte[] buffer = new byte[32768];
    int bytesRead;
    do
    {
        bytesRead = source.Read(buffer, 0, buffer.Length);
         destination.Write(buffer, 0, bytesRead);
    } while (bytesRead != 0);
}

static void Main(string[] args)
{
string SPSite = "https://www.remotewebiste.com";
string dFile = "FileIWantToGet.xlsx"; // a hard coded variable at the momnent...
 
ClientContext _clientContext;
Web _spWebsite;
NetworkCredential cred = new NetworkCredential("user.name", "somePassword", "RemoteDomain");
_clientContext = new ClientContext(SPSite);
_clientContext.Credentials = cred;
_spWebsite = _clientContext.Web;

List list = _spWebsite.Lists.GetByTitle(dFile);
CamlQuery camlQuery = new CamlQuery();
camlQuery.ViewXml = @"<View Scope='RecursiveAll'><Query><Where>
                        <BeginsWith><FieldRef Name='FileDirRef'/>
                            <Value Type='Text'>/subdir0/subdir1/subdir2/subdir3/" + dFile + @"</Value>
                        </BeginsWith></Where></Query></View>";
//camlQuery.FolderServerRelativeUrl = "/";

ListItemCollection listItems = list.GetItems(camlQuery);

_clientContext.Load(listItems, items => items.Include(
    item => item.File.Name,
    item => item.File.ServerRelativeUrl,
    item => item["Proposal_x0020_Navigation_x0020_Grouping"],
    item => item["Modified"]));

_clientContext.ExecuteQuery();// Errors as con't find dfile file

if (listItems != null)
{
    foreach (Microsoft.SharePoint.Client.ListItem item in listItems)
    {
        item.CheckOut(); 
        // shove some data in it and 
 
        item.CheckIn();  

         Console.WriteLine(item.DisplayName);
    }
}
}
}

using System;

using System.IO; using System.Linq; using DocumentFormat.OpenXml.Packaging; using DocumentFormat.OpenXml.Office2013.Excel; using Microsoft.SharePoint.Client; // The following using directive resolves the ambiguity // between the System.IO.File class and Microsoft.SharePoint.Client.File // class. using ClientOM = Microsoft.SharePoint.Client; using System.Net; using System.Data;

class Program { static private void CopyStream(Stream source, Stream destination) { byte[] buffer = new byte[32768]; int bytesRead; do { bytesRead = source.Read(buffer, 0, buffer.Length); destination.Write(buffer, 0, bytesRead); } while (bytesRead != 0); }

static void Main(string[] args)
{
    NetworkCredential cred = new NetworkCredential("USERNAME", "PASS", "WINAD");
    string SPSite = "https://www.COMPANYPORTAL.COM";
    string DirStruc = "/sp/CorporateITPro/BusinessDocuments/Migration/Templates/Master";       
    string dFile = "MigClassification.xslx";
    
    ClientContext clientContext;
    clientContext = new ClientContext(SPSite);
    clientContext.Credentials = cred;
    
    Web spWebsite;
    spWebsite = clientContext.Web;

    List list = clientContext.Web.Lists.GetByTitle(dFile);         
    CamlQuery camlQuery = new CamlQuery();
    camlQuery.ViewXml =("<View Scope='RecursiveAll'><Query><Where><Neq><FieldRef Name='ContentType' /><Value Type='Text'>Folder</Value></Neq></Where></Query></View>");
    camlQuery.FolderServerRelativeUrl = DirStruc;
    
    ListItemCollection listItems = list.GetItems(camlQuery);

    clientContext.Load(listItems, items => items.Include(
        item => item.File.Name,
        item => item.File.Author,
        item => item.File.ServerRelativeUrl, 
        item => item["Proposalx0020Navigationx0020Grouping"], 
        item => item["Modified"])
        );
 
    try
    {
        clientContext.ExecuteQuery();// NOT FOUND ERROR HERE
        if (listItems != null)
        {
            foreach (Microsoft.SharePoint.Client.ListItem item in listItems)
            {
                item.File.CheckOut();
                clientContext.ExecuteQuery();

                // GET SOME DATA RELATED TO THE FILE FROM A DB
                // PUT DATA IN THE FILE

                item.File.CheckIn("", CheckinType.MajorCheckIn);
                clientContext.ExecuteQuery(); 
            }
        }
    }
    catch (Exception ex)
    {
        if (System.Diagnostics.Debugger.IsAttached == true)
        {
            Console.WriteLine(ex.Message);
        }
    }        
}

}