Deep Containment Designs

var location = default(string);
if (vendor != null)
{
    if (vendor.ContactPerson != null)
    {
        if (vendor.ContactPerson.HomeAddress != null)
        {
            location = vendor.ContactPerson.HomeAddress.LineOne;
        }
    }
}

Now, using C# 6, this same idiom becomes much more readable:

var location = vendor?.ContactPerson?.HomeAddress?.LineOne;

http://thebillwagner.com/Blog/Item/2015-03-03-inCWhenpropertiesmightbenull