addBindVarIfThen method
Adds one condition-depended pair of name-value binded to query Sample:
.addBindVarIfThen( user_name!=null, 'user_name', user_name )
Implementation
QueryWithClient addBindVarIfThen(bool cond, String name, value) =>
addBindNameValuePair(BindVarIfThen(cond, name, value));