connection to crm online API by user of office 365

Hi,

I try connection to API crm 2015 online in order to get the service for CRUD message for external application c#.

The connection type is by user of office 365.

When I userd this code I get the error:

Value cannot be null.
Parameter name: identityProvider

Here is the code:            

string webservice_user = Common.GetSettings("CrmUserName");

       string webservice_password = Common.GetSettings("CrmPassword");                

string webservice_uri = Common.GetSettings("CrmUri");            

Uri organizationUri = newUri(webservice_uri);       

Uri homeRealmUri = null;                      

ClientCredentials credentials = newClientCredentials();

credentials.UserName.UserName = webservice_user; 

credentials.UserName.Password = webservice_password;            
OrganizationServiceProxy orgService = newOrganizationServiceProxy(organizationUri, homeRealmUri, credentials, null);

 orgService.ServiceConfiguration.CurrentServiceEndpoint.Behaviors.Add(newProxyTypesBehavior());

 orgService.EnableProxyTypes();   

this.crmService = (IOrganizationService)orgService;           

this.UserId = ((WhoAmIResponse)this.crmService.Execute(newWhoAmIRequest())).UserId;//here I get the exception

Also I tried to use by the example project in SDK Toolkit:

SDK\SampleCode\CS\GeneralProgramming\Authentication\AuthenticateWithNoHelp

with Discovery Address:

https://disco.crm4.dynamics.com/XRMServices/2011/Discovery.svc

And I got The same erorr.

Hope for your help,

Thanks,

Rivky