Question about isNull and fieldname substitution

Jay Keck_vt2xhp

I have multiple field validations that have to be done and I thought I'd just put them in a loop with an array of customfield ids. But the isNull field doesn't seem to accepting my field substitution when building the field name to use as a parameter, it's not detecting null fields. Is what I'm doing below  possible?

string [] fieldids = {"16601"};
for (string fieldid in fieldids) {
    if(isNull("customfield_"+fieldid)) {
       return false,"Field " + getCustomFieldNameById(fieldid) + " must be filled in";
    }
}

Thanks,

Jay

Jay Keck_vt2xhp

Solved my own question. I tried using variable substitution and it worked just fine!

string [] fieldids = {"16601","16805","16810"};
string customfield;
for (string fieldid in fieldids) {
customfield="customfield_"+fieldid;
if(isNull(%customfield%)) {
return false,"Field " + getCustomFieldNameById(fieldid) + " must be filled in";
}
}