CODE EXAMPLE FOR CSHARP

Set value into lookup field in console app using dynamic CRM 365

Account acc = new Account();
acc.Attributes["name"] = "Ram"; // this values got inserted
acc.Attributes["age"] = "22"; // this values got inserted
acc.Attributes["lookupfieldid"] = new EntityReference("contact", contactId); // if lookupfieldid is pointing to contact entityservice.Create(acc); // to create account