Бизнес-инженер

var contactsCount = 0; // количество записей
const string QUERY = @"
<fetch mapping='logical' aggregate='true' version='1.0'>
    <entity name='contact'>
        <attribute name='contactid' aggregate='count' alias='count' />
    </entity>
</fetch>";
var result = service.RetrieveMultiple(new FetchExpression(query));
if (result.Entities.Count > 0)
    contactsCount = (int)result.Entities[0].GetAttributeValue<AliasedValue>("count").Value;