using (var fileInfo = Microsoft.SharePoint.Client.File.OpenBinaryDirect(ctxOriginal, fileServerRelativeUrl))
using (var reader = new StreamReader(fileInfo.Stream))
{
    Microsoft.SharePoint.Client.File.SaveBinaryDirect(
    //Client Context
    ctxTarget,
    // Server relative url of the document
    //listTarget.RootFolder.ServerRelativeUrl + file.ServerRelativeUrl.Replace(libraryServerRelativeUrlOriginal,""),//新路徑
    fileServerRelativeUrlTarget,
    // Content of the file
    reader.BaseStream,
    // Overwrite file if it's already exist
    true);
    ctxTarget.ExecuteQuery();
}

var bookname = item.DisplayName;  
string bookLocation = $"{rootFolder.ServerRelativeUrl}/{bookname}";                                  
var absoluteUrl = new Uri(ctx.Url).GetLeftPart(UriPartial.Authority) + bookLocation;  
var srcUrl = absoluteUrl;  
var destUrl = "https://abc.sharepoint.com/sites/Archive";  
var srcLibrary = "Documents";  
var destLibrary = "Records";  

ClientContext destContext = new ClientContext(destUrl);  
ClientContext srcContext = new ClientContext(srcUrl);  
destContext.Credentials = SPAuth.GetSPOnlineCredentials();  
srcContext.Credentials = SPAuth.GetSPOnlineCredentials();                                 
Web srcWeb = srcContext.Web;  
List srcList = srcWeb.Lists.GetByTitle(srcLibrary);                                 
Web destWeb = destContext.Web;  
destContext.Load(destWeb);  

destContext.ExecuteQuery();  
try  
{  
    Microsoft.SharePoint.Client.File file1 = srcContext.Web.GetFileByServerRelativeUrl(bookLocation);  
    srcContext.Load(file1);  
    srcContext.ExecuteQuery();  
    string location = destWeb.ServerRelativeUrl.TrimEnd('/') + "/" + destLibrary.Replace(" ", "") + "/" + file1.Name;  
    FileInformation fileInfo = Microsoft.SharePoint.Client.File.OpenBinaryDirect(srcContext, file1.ServerRelativeUrl);  
    Microsoft.SharePoint.Client.File.SaveBinaryDirect(destContext, location, fileInfo.Stream, true);  
}  

catch (Exception ex)  
{  
    telemetry.TrackException(new Exception("Failed to copy the book to archive library", ex));  
}