How to use linq extensions with Func parameters in Dynamic Linq expressions?

Extending the dynamic library is certainly an option as already suggested. an alternative given the Where in Dynamic Linq returns an Iqueryable

 public static class DynamicQueryable {

    public static IQueryable<T> Where<T>(this IQueryable<T> source, string predicate, params object[] values) { return (IQueryable<T>) Where((IQueryable) source, predicate, values); }

    public static IQueryable Where(this IQueryable source, string predicate, params object[] values)       {

using a DYnamic Object for the context or repository "locations".
Then use a where which could contain dynamic string predicate and follow with firstOrDefault.
(catch or test for null not considered)

DynamicLocations.Where(x => x.IsPrimaryLocation).FirstOrDefault( ).Address1 as Address;

or dynamic where if needed

DynamicLocations.Where("IsPrimaryLocation",new string[]).FirstOrDefault( ).Address1 as Address;

Details: You can expose on a method on a generic repository Class which you instantiate as a dynamic

     public virtual IQueryable<TPoco> DynamicWhere(string predicate, params object[] values) {
        return AllQ().Where(predicate, values);
    }

Dynamic Generic Repository instantiation Sample

  public class RepositoryFactory<TPoco>  where TPoco : BaseObject,new() {

    public IRepositoryBase<TPoco> GetRepository(DbContext context) {

       // get the Pocotype for generic repository instantiation
        var pocoTypes = new[] {typeof (TPoco)};  // but supports <T,U>
        Type repBaseType = typeof (RepositoryBase<>);

        IRepositoryBase<TPoco> repository = InstantiateRepository(context, repBaseType, pocoTypes);

        return repository;
    }


    private IRepositoryBase<TPoco> InstantiateRepository(DbContext context, Type repType, params Type[] args) {

        Type repGenericType = repType.MakeGenericType(args);
        object repInstance = Activator.CreateInstance(repGenericType, context);
        return (IRepositoryBase<TPoco>)repInstance;
    }

}