c# Lambda Expression built with LinqKit does not compile
- by Frank Michael Kraft
This lambda does not compile, but I do not understand why.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using LinqKit;
namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
var barModel = new BarModel();
string id = "some";
Console.WriteLine(barModel.subFor(id).ToString());
// output: m => (True AndAlso (m.key == value(ConsoleApplication2.Bar`1+<>c__DisplayClass0[ConsoleApplication2.Model]).id))
Console.ReadKey();
var subworkitems = barModel.list.Where(barModel.subFor(id).Compile());
// Exception {"variable 'm' of type 'ConsoleApplication2.Model' referenced from scope '', but it is not defined"}
Console.WriteLine(subworkitems.ToString());
Console.ReadKey();
}
}
class Bar<TModel>
{
public Bar(Expression<Func<TModel, string>> foreignKeyExpression)
{
_foreignKeyExpression = foreignKeyExpression;
}
private Expression<Func<TModel, string>> _foreignKeyExpression { get; set; }
public Expression<Func<TModel, bool>> subFor(string id)
{
var ex = forTargetId(id);
return ex;
}
public Expression<Func<TModel, bool>> forTargetId(String id)
{
var fc = _foreignKeyExpression;
Expression<Func<TModel, bool>> predicate = m => true;
var result = predicate.And(m => fc.Invoke(m) == id).Expand();
return result;
}
}
class Model
{
public string key;
public string value;
}
class BarModel : Bar<Model>
{
public List<Model> list;
public BarModel() : base(m => m.key)
{
list = new List<Model>();
}
}
}
