LINQ IQueryable: Set 1 Parameter to accept Where Clause - linq

Question

sample code
public class program
{
public void sample()
{
var qry = repo.All(); // returns IQueryable //came from EF
var keyword = "al";
var result = qry.DynamicFilter(keyword, filterconditions);
// it should return all persons with 'al' in their name and nickname
}
public List<Expression<Func<Person, string, bool>>> filterconditions
{
get
{
var ret = new List<Expression<Func<Person, string, bool>>>();
ret.Add((m,n) => m.Name.Contains(n));
ret.Add((m,n) => m.Nickname.Contains(n));
return ret;
}
}
}
this is my extension
public static class linqExt
{
public static IQueryable<T> DynamicFilter<T>(this IQueryable<T> qry, string keyword, IEnumerable<Expression<Func<T, string, bool>>> conditions) where: T
{
var ret = qry;
foreach(var item in conditions)
{
ret = ret.Where(m => item.Compile()(m, keyword));
}
return ret;
}
}
is there any way to implement this without using the Compile/Invoke??
ret = ret.Where(m=> func.Compile()(m, keyword));??
the problem is that I can't use the Compile because the collection is an IQueryable and i can't convert it to IEnumarable because if I do that it will pull all the data from database.
I am thinking if I can use the METHODS and PROPERTIES of the EXPRESSION class
any guest? thanks

Answer 1

We have done something similar; but we use the PredicateBuilder class presented here: https://petemontgomery.wordpress.com/2011/02/10/a-universal-predicatebuilder/
var filter = PredicateBuilder.True<Person>()
.And(m => m.Name.Contains(n))
.And(m => m.Nickname.Contains(n));
Then you can just do qry.Where(filter) and it will apply your "dynamic" where clause. If this is LinqToEF this will cause the Where() clause to actually be generated and executed in SQL, which is probably want you want.
The PredicateBuilder is a very powerful class, and you can build some very elaborate clauses. When you need to do "ORs", be sure and "start" with a PredicateBuilder.False<Person>() statement.
You can also do conditional logic, and "append" statements to your filter, for example:
if (lookingForReallyLongNames == true)
{
filter = filter.And(m => m.Name.Length > 15);
}