c# - Nesting PredicateBuilder predicates : 'The parameter 'f' was not bound in the specified LINQ to Entities query expression' -

i building predicates using linqkit's prediatebuilder class dynamically setup filters , i want combine nested 1 another.

i have read (http://www.albahari.com/nutshell/predicatebuilder.aspx) :

here code :

// main predicate. var mainpredicate = predicatebuilder.true<document>();  // ... other conditions main predicate here ...  // inner predicate (combined conditions using or). var innerpredicate = predicatebuilder.false<document>();  foreach (var period in periods) {     var p = period;     innerpredicate =         innerpredicate.or(             d =>             (d.date >= p.datefrom && d.date <= p.dateto)); }  mainpredicate = mainpredicate.and(innerpredicate);  documents = this.objectset.asexpandable().where(mainpredicate).tolist(); 

i combining 2 predicates explained in documentation. however, exception :

the parameter 'f' not bound in specified linq entities query expression

i first thought inner predicate has expanded before combining main predicate, changed combining code add call to inner predicate's expand method :

mainpredicate = mainpredicate.and(innerpredicate.expand()); 

but exact same exception.

the difference in code versus documentation dynamically build nested predicate using foreach loop. don't know how can negatively affect resulting expression.

• what wrong code ?

• how can debug ?

• where f parameter comes ? how generated ? why problematic in case ?

• is there kind of expression tree visualizer of kind me see wrong resulting expression ? because expression's body hard read.

finally, have found way avoid combining multiple predicates main expression tree.

given each predicate represents different filter , want final, combined filter series of must-be-respected conditions, can each of predicates has return true final predicate return true.

for work, predicates has combined and. so, resulting sql query must :

predicate1 , predicate2 , predicate3 ...

a better way combine these predicates and chain where query operators final query, :

var documents = this.objectset.asexpandable()     .where(mainpredicate)     .where(otherpredicate)     .where(yetanotherpredicate)     .tolist(); 

the resulting sql query combine each of these predicates and. wanted do.

it easier hacking out expression tree myself.