Applying OrganizationServiceProxy when connecting to CRM Dynamics On-line

I'm connecting successfully to on-premise server using the organization service by this code.

using (OrganizationServiceProxy proxy = new OrganizationServiceProxy(
  Organization, 
  HomeRealm, 
  CredentialsForClient, 
  CredentialsForDevice)) { ... }

Organization is our server plus the suffix OrgName/XRMServices/2011/Organization.svc. CredentialsForClient is my log-in (or my live ID when going for on-line). HomeRealm and CredentialsForDevice are set to null.

This appears to work perfectly for on-premise version but when I go on-line, I get an error. I can create the proxy variable but when I attempt to execute the code below, the exception tells me that I can't have a null value as an end point. This is hardly telling me anything, due to my ignorance.

EntityCollection entityCollection = proxy.RetrieveMultiple(fetchExpression);

Of course I'm using a different Organization when going on-line. I copied the string from the settings of our on-line version of CRM Dynamics (just as I did for the on-premise version). How can I tackle this problem?

Solution

Have you seen this sample, it shows how to Authenticate Users with Microsoft Dynamics CRM Web Services without any helper code for all types of connection, on-premise, on-line.