Check , Attribute is not available in entity using IF condition

I can retrieve the entity in objRecord variable.

Entity objRecord = service.Retrieve(<here retrieve>)

If the value available in new_fieldname it will return in objRecord . so i will check like the following,

if (objRecord .Attributes.Contains("new_fieldname"))
{

}

How can I check the new_fieldname  Does not have value? don't want to check in else part  i need to check only in IF condition? how can I do this ? Is it possible ?