Programmatically add item to sharepoint list from window application

how about following msdn? try using ClaimClientContext.GetAuthenticatedContext instead

string targetSite = "http://SharePointServer/";
using (ClientContext CNX = ClaimClientContext.GetAuthenticatedContext(targetSite))
{
            //Load Libraries from SharePoint
            CNX.Load(CNX.Web.Lists);
            CNX.ExecuteQuery();

            using (FileStream fs = new FileStream(fileName.ToString(), FileMode.Open, FileAccess.Read))
            {

                Microsoft.SharePoint.Client.File.SaveBinaryDirect(CNX, "/" + "Shared Documents" + "/" + System.IO.Path.GetFileName(fileName.ToString()), fs, true);
            }
        }

http://msdn.microsoft.com/en-us/library/hh147177(v=office.14).aspx

if it doesnt work and still returns a 403 than it has to be an issue with ADFS not setup properly! check and refer to this:

http://blogs.technet.com/b/speschka/archive/2010/06/04/using-the-client-object-model-with-a-claims-based-auth-site-in-sharepoint-2010.aspx

EDIT

after some digging about i did find this:

http://stackoverflow.com/questions/11295953/claim-auth-from-adfs

they have a similar issue to you and required authentication from adfs! the issue is its complex and so he made a quick bolg on his findings:

http://jwillmer.de/blog/2013/01/04/sharepoint-online-with-adfs-authentication/

his solution :

https://github.com/jwillmer/SharePointAuthentication

Please make sure that your Build Configuration for your windows application is set to

Platform Target: (Any CPU)

or

Platform Target (x64)

in Project Properties --> Build --> General in Visual studio

For setting permissions on ClientContext:

CNX.Credentials = new NetworkCredential("user", "password", "domain");

or

CNX.Credentials = CredentialCache.DefaultCredentials;

Also, have you seen this blogpost? It has some helper dll that seems to be helpful