How to obtain a list of documents from a SharePoint library that were created X days ago using CSOM

In case you ever need to generate a list of documents contained in a SharePoint library that were created, say, 30 days ago or earlier, here is one way that you might go about doing that using CSOM:

using (ClientContext context = new ClientContext(@"https://webApplicationName/siteName"))
{
    context.Credentials = System.Net.CredentialCache.DefaultCredentials;
                    
    List documentsLibrary = context.Web.Lists.GetByTitle("Documents");
                    
    CamlQuery query = new CamlQuery();
    query.ViewXml = "<View><Query><Where><Leq><FieldRef Name='Created'/><Value Type='DateTime'><Today OffsetDays='-30' /></Value></Leq></Where></Query></View>";
         
    //CamlQuery query = CamlQuery.CreateAllItemsQuery();
    ListItemCollection expiringDocs = approvedDocumentsLibrary.GetItems(query);
                   
    context.Load(expiringDocs);
    context.ExecuteQuery();

    foreach (ListItem document in expiringDocs)
    {
        Console.WriteLine(string.Format("{0}", document["Title"]));
    }
}

You'll notice that the crux of the filtering operation is dependent on the XML contents contained in my CamlQuery object as follows:

<View><Query><Where><Leq><FieldRef Name='Created'/><Value Type='DateTime'><Today OffsetDays='-30' /></Value></Leq></Where></Query></View>

with the <Today> element being the key to this in order to take the current date and offsetting it by 30 days in the past.

CAML Queries always take a bit of trial and error in order to get them right so I hope this helps save you some time!

Possible solution for resolving a 409 Conflict Error when uploading a file to a SharePoint 2013 site using CSOM

I was just attempting to upload a file to one of my SharePoint 2013 sites using CSOM when I ran into a 409 Conflict error.  A simplified version of the code I was using is as follows:

using Microsoft.SharePoint.Client;
using Microsoft.SharePoint.Client.Publishing;
using Microsoft.SharePoint.Client.Publishing.Navigation;
using Microsoft.SharePoint;
using System.IO;
...
using (ClientContext context = new ClientContext(@"https://webapplicationname/sitename"))
{
   context.Credentials = System.Net.CredentialCache.DefaultCredentials;
   using (FileStream fs = new FileStream(@"c:\docs\sample.doc", FileMode.Open))
   {
      Microsoft.SharePoint.Client.File.SaveBinaryDirect(context, @"/Documents/sample.doc", fs, true);
   }
}

One major thing I'd like to highlight in the code above is that I was trying to set the context to reference a subsite that is located under the root site collection.  After a bit of experimentation, I actually stumbled onto the solution which is as follows:

using (ClientContext context = new ClientContext(@"https://webapplicationname"))
{
   context.Credentials = System.Net.CredentialCache.DefaultCredentials;
   using (FileStream fs = new FileStream(@"c:\docs\sample.doc", FileMode.Open))
   {
      Microsoft.SharePoint.Client.File.SaveBinaryDirect(context, @"sitename/Documents/sample.doc", fs, true);
   }
}

In the code that worked, notice that I set the context to reference the root site collection and then used the second parameter in the SaveBinaryDirect method call to specify the relative path to the document library on the site in question.  At that point, the code worked perfectly and I was able to upload the document to the site's document library without any issues.

Hopefully, this may help solve your problem as well.