using System;
using System.Linq.Expressions;
using System.Data.Entity;
using System.Linq;
public class Program
{
static void SomeDbRequest(Expression<Func<Person, bool>> condition, Expression<Func<DbEntities, Person, bool>> advancedCondition)
{
using (DbEntities db = new DbEntities())
{
var query = db.Set<Person>().AsQueryable();
var result1 = query.Where(condition).ToList();
//это работает
var result2 = query.Where(x => advancedCondition.Compile().Invoke(db, x));
//это нет
//NotSupportedException: 'LINQ to Entities' erkennt die Methode 'Boolean Invoke(DbEntities, Person)' nicht,
//und diese Methode kann nicht in einen Speicherausdruck übersetzt werden.
}
}
static void Main(string[] args)
{
Expression<Func<Person, bool>> c1 = p => p.Name == "Peter";
Expression<Func<DbEntities, Person, bool>> c2 = (db, p) => db.Set<Event>().Any(e => e.Author == p.Name);
SomeDbRequest(c1, c2);
}
class DbEntities : DbContext { }
class Person
{
public string Name { get; set; }
}
class Event
{
public string Description { get; set; }
public string Author { get; set; }
}
}
